AACS Regents Physics
Labs Page
|
|
PRE-LAB DISCUSSION:
During the year you will develop your skills at problem solving and working effectively as part of a team. This lab will give you the opportunity to practice these skills.
PURPOSE:
To design and construct the tallest free standing tower from a single sheet of paper and 30 cm of tape.
MATERIALS:
1 sheet of white paper
1 sheet of colored paper
30 cm plastic tape
scissors
PROCEDURE:
1. Each student will receive 1 sheet of white paper. Use the white sheet to try out various design possibilities. Think wildly!
2. Each lab group will receive one sheet of colored paper for their competition tower.
3. Before beginning with the colored paper, examine the designs of each group member.
4. Decide which aspects of each design should be incorporated into your final design. The most important aspects of a winning team are communication and cooperation.
OBSERVATIONS AND DATA:
1. Look at the designs form the other groups. Describe how they are similar.
2. Look at the designs form the other groups. Describe how they are different.
CONCLUSIONS AND QUESTIONS:
1. What were the limiting factors in your tower's construction.
2. Did your group work well as a team? What could you do differently to be more effective?
PRE-LAB DISCUSSION: Whenever measurements are made, it is important to tell how well the measurements were taken. One way to express the quality of an experimental technique is to restrict the amount of numbers in a measurement. The way scientists accomplish this is by using the correct amount of significant figures in the measurements they make. Before you begin this lab carefully read the sections in your text on significant figures (p. 22-25) and the section on data tables (p.26).
PURPOSE:
To develop skills needed to properly collect and display data.
MATERIALS:
Meter stick student desk pencil
PROCEDURE:
1. Each member of your lab group should independently measure the length and width of your desk top using the correct number of significant figures based on your measuring device. Don't tell each other what your values were. You may want to repeat those measurements a few times to be sure. Record your measurements.
2. Now compare your result with others in your lab group. Discuss any discrepancies and remeasure if necessary. As a group decide on the best values for the dimensions of the desk top and record them in the "Observations and Data" section of your lab report.
ANALYSIS:
3. Using the significant figure rules for calculations, compute the area of the desk and record your calculations in the "Calculations" of your lab report.
4. Construct a data table for this experiment and include it in the "Observations and Data" section of your lab report.
CONCLUSIONS AND QUESTIONS: Write the full sentence answers to the following questions in your "Conclusions Section".
1. Compare your group's area with other groups. Since tables were precision milled by the same company, they should be identical but they are not. Which area do you think is correct? Why? Can the class agree upon the proper value for the area?
2. Three students each measure a separate section of a piece of wood and come up with the following data, what is the total length of the wood? 2.5 cm, 0.452 dm, 157.3 mm.
3. What is the density of a 7.58 g object that has of volume of 3.9 cm3?
PURPOSE:
To make measurements correctly, and to use graphical relationships to make predictions.
PRE-LAB DISCUSSION:
When making measurements, scientists must use the measuring devices correctly so that when they compare data they can be certain that the same techniques were used to obtain it. If the data is trustworthy, it may then be analyzed to make predictions or to draw conclusions.
MATERIALS:
3 pieces of electrical wire (5-30cm)
3 rectangular pieces of floor tile
1 triangular piece of floor tile
balance
metric ruler
graph paper
PROCEDURE:
1. Measure the length of the three wires. (Remember: The smallest division on the metric ruler is 1 millimeter, so that you should read millimeters directly and estimate to the nearest tenth of a millimeter. Keep this in mind when using other measuring devices.)
2. Measure the mass of the wires (following rules for the use of measuring devices).
3. Record the data obtained in procedures 1 and 2 in a neat table.
4. Measure the length, width and mass of each rectangular piece of floor tile.
5. Record your measurements in another neat data table.
ANALYSIS:
1. Determine the area of each rectangular piece of tile and record this value in the data table. Show the setups for your calculations in the "calculations" section of your lab report.
2. Make a graph of mass (y axis) versus length (x axis) of the wire. Include the units on the graph.
3. Use the longest and shortest wire to determine the equation for the line on the mass vs. length graph.
4. Use the equation to predict the length of the medium wire. How closely does it agree with the your results?
5. Make a graph of mass (y axis) versus area (x axis) for the rectangular pieces of tile.
6. Determine the equation of the line obtained in the area vs. mass graph.
7. Measure the area of the triangular piece of tile and use the graph (the line equation) to predict its mass. Include the calculations for this prediction in the calculation section of your lab report.
CONCLUSIONS AND QUESTIONS:
1. Did your graphs pass through the origin? Should they have? Explain why or why not.
2. Calculate the slope of each graph (include the units).
3. Explain the meaning of each slope.
4. How may this method of prediction be used in a real-life situation?
BACKGROUND INFORMATION:
The recording timer is a device that will help you study motion. It consists of a simple electric bell-type vibrator through which a paper tape may be drawn. Carbon paper between the vibrating arm and the paper tape leaves a mark on the tape each time that the arm goes up and down. When connected to a dry cell, this arm vibrates regularly like the pendulum on a grandfather clock, except faster!
If the period of the timer was known, and if the paper tape was attached to some moving object, one could simply measure the distance between dots and the distance the object traveled in the amount of time for one period would be known. This may be very useful for future labs.
PURPOSE:
To determine the period of a recording timer (find out how long it takes for the vibrating arm to go all the way up and all the way down once).
GENERAL DIRECTIONS:
•Brainstorm with your lab group and come up with a few ways the period may be found.
•Decide which procedure would be best and write it down on a sheet of paper.
•Have your procedure approved by your lab instructor.
•Carry out your procedure, keep in mind that you should do at least three trials for validity.
•Make your measurements carefully always using rules for the use of measuring devices.
•Construct a data table and report your findings. Carry out any calculations using significant figure rules and include all calculations in your lab report.
•Write your lab report using the guidelines provided in the lab packet that you received at the beginning of the year.
•You may copy the "Purpose" above and steal some information for your "Pre-Lab Discussion" from the background information above.
CONCLUSIONS AND QUESTIONS:
1. Based on your results, what is the period of a recording timer?
2. Compare your results to those of other lab groups, how do your results compare with theirs?
3. If someone were to carry out your procedures, between what range of values would you guarantee that their results would fall?
4. What is the frequency of the timer (how many times does it vibrate per second)? How does the frequency of the alternating current (60 Hz) in this classroom compare to your value?
BACKGROUND INFORMATION:
From the activities you did in class you should have an understanding of the significance of the slope of the displacement/time curve. You will use your knowledge to describe the motion of a toy car.
PURPOSE:
To make and interpret a graph of the motion of a toy car.
GENERAL DIRECTIONS:
-The motion of the car should be studied for between one and three meters.
-The data you collect should be divided into at least ten intervals of displacement and /or time.
-Brainstorm with your lab group and come up with a few ways to collect the data.
-Have your procedure approved by your lab instructor. (Use the worksheet provided on the back if you wish.)
ANALYSIS:
-After collecting your data and recording it in a neat table, graph displacement (y-axis) versus time(y-axis).
-Determine the slope of the graph for any portion of it that appears to be somewhat straight.
-Give a qualitative description of the car's motion based on your data.
PRE-LAB DISCUSSION:
By gathering data on the change in displacement over time that an object travels, it is possible to determine the object's acceleration.
PURPOSE:
To determine the acceleration a person experiences as he/she coasts down a hill in an automobile.
MATERIALS:
automobile stopwatch chalk
gentle hill measuring tape or meter stick
PROCEDURE:
1.Set up a data table with headings like the one below and include it in the "Observations and Data" section of your lab report.
|
Trial |
|
|||||||||
|
5 m |
10 m |
15 m |
20 m |
25 m |
30 m |
35 m |
40 m |
45 m |
50 m |
|
2. Go outside and select a paved hill which has a constant, gentle slope.
3. Use chalk to mark a starting line across the top of the hill.
4. Draw five more lines across the hill, the first one 5 m from the starting line, and each consecutive one 5 m from the one before it.
5. Select a rider who will ride the car down the hill. Let the rider start from rest at the starting line and ride the car to the first line. Time how long it takes to travel the 5 m. Record the time for at least three trials and record the time in the data table. Omit any trials in which the rider didn't coast in a straight line, pushed off at the start, or did anything that would affect the data.
6.Record the time for the rider to travel from the start to each of the remaing lines.
ANALYSIS:
1. Plot the displacement vs. time on a sheet of graph paper.
2. Calculate the average velocity per interval and plot velocity vs. time on another graph.
CONCLUSIONS AND QUESTIONS:
1. Based on the displacement time graph, was the rider accelerating? Explain.
2. Calculate the acceleration of the rider for any portions of the velocity/time graph where there was a constant slope?
3. Was there any indications that the rider did not accelerate at a constant rate. What might be some reasons for this?
PRE-LAB DISCUSSION:
Although the path of a football may seem to be complex it is actually quite simple when the effects of friction are small. The horizontal velocity is constant . The vertical velocity always changes by 9.8 m/sec. every sec.
PURPOSE:
To determine the velocity with which you throw a football.
MATERIALS:
Football stopwatch paper
pencil calculator measuring tape
PROCEDURE:
1. Take all of your materials out to the football field.
2. Select a thrower, a timer, and a marker.
3. Throwers should toss the ball around to loosen up the arm muscles.
4. The thrower should stand at a marked line. The marker should move downfield and stand at a place where he/she feels the ball might land.
5. The thrower should stand at the line and throw while the timer times the length of time the ball is in the air, the marker should mark where the ball lands and the distance should be measured and recorded.
OBSERVATIONS AND DATA:
Record the following measurements in the "Observations and Data" section of your lab report:
Time in air: (sec.)
Horizontal displacement: (meters)
ANALYSIS:
Perform the following calculations in the "Calculations " section of your lab report:
1.Determine the value for vh
2. Determine the value for viy.
3. Draw a vector diagram like the one below and record the values in calculation 1 and 2 on it as shown.
4. Use the Pythagorean Theorem to find the value of vi
5. Use trigonometry to find the angle with the horizontal at which the ball was thrown.
CONCLUSIONS AND QUESTIONS:
Discuss your results with other groups to determine:
1. What relationship exists between vi and the horizontal displacement?
2. What relationship exists between the angle the ball is thrown at and horizontal displacement?
3. Why might a kickoff at a football game be made at a different angle than a punt?
PRE LAB DISCUSSION: When two or more forces act simultaneously at the same point, they are said to be acting concurrently and are called concurrent forces. In this investigation you will apply three forces at the same time to an object. Since the object will not be moving the system must be at equilibrium. You will determine the vector sum of two of the concurrent forces (the resultant) and investigate the relationship of the resultant to the third force.
PURPOSE: To apply the laws of vector addition.
MATERIALS:
force board large white paper ruler
protractor sharp pencil
PROCEDURES:
1. Obtain the force board and 3 scales. check each scale to make sure the needle points to zero when no load is attached. Attach the scales to the force board so that each scale registers a force midrange on the scales.
2. Place a large piece of paper he spring scale arrangement. Using a sharp pencil, carefully mark two points along the line of action of each force.
3. Remove the paper and using the points you marked, construct lines A,B and C.
4. Record the reading of each spring scale next to the corresponding line.
5. Using a suitable number scale, construct vectors along lines A, B, and C to represent each force. If the spring scales are not calibrated in newtons, you can use the readings in grams or kilograms to represent the force because the readings in kilograms are directly proportional to newtons.
ANALYSIS:
1.Add vector A to vector B by drawing A parallel to itself but with its tail at the head of B.
2. Draw a vector representing the vector sum of A+ B, the resultant. Evaluate the magnitude of this resultant in terms of the number scale used.
3. On a separate sheet of paper, reconstruct the vectors, A, B, and C and add them. Do this by placing a piece of paper over your first diagram and tracing the vectors. Place the tail of B at the head of A and d then the tail of C at the head of B.
CONCLUSIONS AND QUESTIONS:
1Compare the magnitude and the direction of the resultant force of A + B with the magnitude of force C. Explain your findings.
2.Describe the results of your addition of A + B + C in Analysis 3. Explain.
3.Suppose that you had added B to C. What resultant would you expect?
4. What resultant would you expect if you added C to A?
5. Based on your answer to the previous question, do you think that the commutative property applies to vector addition? Explain why.
PRE-LAB DISCUSSION:
According to Newton's Laws of Motion, an object does not accelerate unless acted upon by an unbalanced force. There may be some relationship between the amount of this force and the acceleration that it produces.
PURPOSE:
To determine the relationship between force and acceleration on a given mass.
MATERIALS:
laboratory cart set of metric masses recording timer
timer tape carbon paper discs pulley
large paper clip washers string
PROCEDURE:
Note: If using PASCO Carts and timers use procedures given by instructor.
1. Load the cart with the following masses: 50 g, 100 g, 200 g. Attach one end of the string and pass it over the pulley. Hang metal washers or small weights on the clip until the friction force acting on the cart is just offset. Forces due to friction are offset when you can give the cart a very slight push and it moves at a constant speed across the table. Do not remove this added weight.
2. Pull the end of the timer tape through the timer and attack it to the cart as indicated in the diagram. For the first trial, remove the 50 g. mass from the cart and hang it on the end of the string.
3. Start the timer and release the cart. Stop the timer and the cart when the 50 g mass reaches the floor. Remove the timer tape and label it "50 g trial" on the end that was attached to the cart (the start).
4. Remove the 50 g mass from the string and put it back on the cart (The total mass of the system must remain constant). Remove a 100 g mass from the cart and place it on the end of the string. Make and label a second tape in the same way as you made the first tape.
5. Repeat steps 2 and 3 for 150 g, 200 g, and 250 g masses (as a result increasing the mass added by 50 g each time). Be sure to place each mass back on the cart after using it.
ANALYSIS:
Note: If using PASCO Carts and timers use analysis #6 only!
1. Since the timer undergoes regular vibration, rather than measuring time in seconds, a set of vibrations of the timer may be used as a unit of time. For this lab 5 oscillations of the timer will represent a unit of time called a "tock". Label the first distinguishable dot on each tape zero. Label every fifth dot after that 1, 2, 3, and so on.
2. Since two consecutive numbered dots represents a time interval, and since the tape was attached to the cart, the distance between two dots represents the average velocity of the cart during the time interval (v = d/t, and t = 1 tock).
3. Make a table with headings like the ones below. Measure each distance on each tape carefully and record all values in the table as velocities. Do this for about the first ten "tocks" on each tape.
|
(tock) |
|
||||
|
Tape 1 |
Tape 2 |
Tape 3 |
Tape 4 |
Tape 5 |
|
4.On the same graph, make a velocity versus time plot for each tape. Plot velocity on the vertical axis, and time on the horizontal axis. When you plot the points use a "best fit line" for the graph (do not "connect dots"). If you are making your graphs by had use colored pencils to distinguish one tape from another.
5. The slope of a velocity-time graph is Æv/Æt which is the acceleration. Determine the slope of each of the lines on your velocity-time graph. Make a table with headings like the ones below. Record your values next to the weight of each mass that accelerated the cart.
|
|
|
6.Plot the graph of the acceleration versus force with acceleration on the horizontal axis. Draw a best fit line.
CONCLUSION QUESTIONS
1.Explain the meaning of the second graph. (If PASCO carts were used, explain the meaning of the graph)
2.Does this relate to Newton's second law? Explain
3. Calculate the slope of the graph, analyze the units of the slope. What should the slope represent? How well does the value of the slope agree with the value you would expect to get based on your data?
PRE LAB DISCUSSION: We are aware of the frictional force that opposes the motion of one surface in contact with another. When there is a sheet of ice on a sidewalk, the friction is reduced, and it is difficult to walk. The lack of friction is an inconvenience. However, machines are lubricated to reduce friction where it is not an advantage.
If you pull an object horizontally at constant velocity. the applied force just balances the frictional force. you will perform a series of short experiments in which you vary one property of the two surfaces in contact and measure the force necessary to move an object at constant velocity.
PURPOSE: To determine the effect of certain surface conditions on the force of friction.
MATERIALS:
string 5 bricks wrapping paper waxed paper sandpaper
plastic wrap spring scale dynamics cart tape
PROCEDURES:
A. Nature of the Surfaces
1. Make a table with the following headings and include it in the "Observations and Data" section of your lab report.
|
Type of Paper |
Force (N) |
2. Wrap the brick in brown wrapping paper. Tie a string around the brick so that the string does not interfere with the sliding surface.
3. Practice until you can pull the brick with constant velocity. Have your partner read the spring scale while the brick is in motion. Record the force in the data table. make sure you pull with the scale in a horizontal position each time.
4. Vary the surface by wrapping the brick with different kinds of paper. Repeat step 3. Try to move the brick with constant velocity.
B. Surface Area
1. Make a table with the following headings and include it in the "Observations and Data" section of your lab report.
|
Area |
Force (N) |
2. Position the brown wrapped brick with its largest surface in contact with the table. Measure the force necessary to pull the brick across the table at constant velocity. Record your results in the table. Be sure to make readings while the brick is moving uniformly.
3. Turn the brick on one of its narrow edges and measure the force as in step 2. (You may have to relocate the string.) Record your measurements.
4. Try this again, this time with the brick standing on end if possible.
C. Starting Motion vs. Maintaining Motion
1. Make a table with the following headings and include it in the "Observations and Data" section of your lab report.
|
Motion |
Force (N) |
2. Measure the force needed to start the paper-wrapped brick moving. Then measure the force needed to keep it moving uniformly. Record your readings in the table.
D. Speed of Motion
1. Make a table with the following headings and include it in the "Observations and Data" section of your lab report.
|
Velocity |
Force (N) |
2. Measure and record in the table the force necessary to move a brick uniformly at different velocities.
E. Rolling and Sliding Motion
1. Make a table with the following headings and include it in the "Observations and Data" section of your lab report.
|
Motion |
Force (N) |
2. Tape the wheels of the dynamics cart so that it will slide rather than roll when pulled. Measure the force needed to make it move at constant velocity. Then remove the tape and measure the force necessary to roll the cart at constant velocity. Record your observations in the table.
F. Force Pressing the Surfaces Together
1. Make a table with the following headings and include it in the "Observations and Data" section of your lab report.
|
Number of Bricks |
Force (N) |
2. Measure and record the force needed to slide the paper-wrapped brick uniformly across the table.
3. Place another brick on top of the first brick and repeat the procedure.
4. Repeat the procedure, adding bricks until you have measured the force necessary to move five bricks.
ANALYSIS:
1. Construct a graph from the data obtained from procedure F.
CONCLUSIONS AND QUESTIONS:
1. Which factors influence the force of friction?
2. List three examples where friction helps you and three where friction is a hindrance.
3. What did you learn from this investigation about the cause of the frictional force?
4. What is indicated by the slope of the graph that you made?
PRE LAB DISCUSSION: When a block rests on an inclined plane, its weight, concentrated at the center of gravity of the block, acts vertically downward. Since the block cannot move in that direction, the weight of the block is resolved into two component forces. One component , Fp, acts parallel to the plane and tends to slide the block down the plane. The other component, Fn, acts at right angles to the plane and tends to make the block stick to the plane. If the slope of the plane is great enough to cause the block to slide at uniform speed, the ratio of the parallel force to the perpendicular force is the coefficient of sliding friction between the block and the plane.
The coefficient of friction may be found experimentally by weighing the object and then using a spring balance to measure the force needed to slide the object at a slow uniform speed. The coefficient of friction depends upon the nature of the two surfaces in contact.
PURPOSE: To determine the coefficient of sliding friction.
MATERIALS:
string wooden board for inclined plane
protractor block, smooth on one side, sandpaper on the other side
spring balance meter stick
lab balance
PROCEDURES:
1. Make a table with the following headings and include it in the "Observations and Data" section of your lab report.
|
Fp |
ø |
2. Place the incline flat on the table. Place the wooden block on top of it smooth side down. Tie a string on the block and, using your spring scale, measure the force needed to drag it across the board at a slow, constant speed. Record this in your table as Fp for trial 1.
3. with the block resting on the board, increase the pitch of the plane gradually until a grade is reached at which the block will slide slowly down the plane with uniform speed when it is given a gentle push. Record this as q for trial 1.
4. Repeat Procedures 2 and 3 for two more trials.
5. Repeat Procedures 2 through 4 this time using the sand paper side of the block.
6. Use the lab balance to determine the mass of the block and record this in the "Observations and Data" section of your lab report.
ANALYSIS:
1. Calculate the weight of the block.
2. Determine the average of q and Fp for the three trials for the smooth side and then calculate the averages for the three trials for the sandpaper side.
3. Using the known value of the weight and q, calculate Fn for h sides of the block.
4. Using your values for W and Fp, calculate the coefficient of friction (µ).
CONCLUSIONS AND QUESTIONS:
1. Using your values for W and Fn calculate the theoretical value of Fp for the smooth side of the block.
2. Calculate the percent error between the observed value of Fp and the theoretical value.
3. Using your value from question 2, assign what is your coefficient of friction for the smooth side of the block with a plus/minus value attached.
4. Within the limits of error, how well does your value for coefficient of friction agree with the values obtained by other groups. Explain why.
PRE LAB DISCUSSION: When a ball rolls down a ramp it has a certain amount of momentum when it reaches the bottom. If the ramp is suspended a certain distance above the floor, the horizontal displacement of the ball may be used to represent its momentum (if it had a greater velocity it would travel farther in the horizontal direction). If a ball strikes another one at the bottom of the ramp, it imparts some of its momentum to the second ball. The laws of vector addition provide a method for comparing the momentum of the single ball rolling off the ramp, to the combined momentum of two balls after the first one strikes the second one.
PURPOSE: To test the law of conservation of momentum, and to verify that momentum is a vector quantity.
MATERIALS:
collision in two dimension set meter stick tracing paper
C-clamp masking tape carbon paper
protractor (and compass)
PROCEDURES:
1. Clamp the ramp to the table so that the set-screw is beyond the edge of the table.
2. Adjust the position of the set-screw so that it is directly in front of the ramp.
3. Roll a ball from the top of the ramp and check to be sure that the height of the set-screw is just enough for the ball to clear it.
4. Attach the plumb line to the set screw so that the plumb bob just touches the floor directly below the set-screw.
5. Tape four pieces of carbon paper , to form a large sheet measuring about 44 cm by 56 cm. Do the same with four sheets of tracing paper.
6. Put the carbon paper on the floor carbon side up with the tracing paper directly over it.. Position the paper in such a way that the center of one end of the paper is just below the plumb bob. Tape the paper in place. Mark the point below the bob on the paper. Label this point o.
7. Without placing the target sphere on the set-screw, starting from the top, roll a steel sphere down the ramp several times. Dots will appear on the tracing paper where the sphere lands. Circle this cluster of points and label it "total".
8. Adjust the position of the set-screw so that when a sphere is placed on it, the incident sphere will strike it at and angle.
9. using the steel sphere as an incident sphere and a steel sphere of equal mass as a target sphere, try several collisions. Be sure that you start the incident sphere from the same point at the top of the ramp each time.
10. Circle the cluster of points where the incident sphere lands and label it I1, and circle the cluster of points where the target sphere lands and label it T1.
11.Change the position of the target sphere and repeat steps 9 and 10. This time however, circle the cluster of points where the incident sphere lands and label it I2, and circle the cluster of points where the target sphere lands and label it T2.
ANALYSIS:
1. Using the meter stick, draw a vector from the zero point to to the center of the cluster of points labeled "total". This represents the total momentum of the incident sphere before the collision. Label this vector po.
2. Draw a vector from the zero point to o the center of the cluster of points labeled T1. Label this vector pt1.
3. Draw a third vector from the zero point to to the center of the cluster of points labeled I1. Label this vector pi1.
4. Use vector addition to add vector pt1 to vector pi1.
5. Repeat steps 2-4 for the points in I2 and T2.
6. Make a sketch of your results on a sheet of paper and include it in the "Observations and Data" section of your lab report.
CONCLUSIONS AND QUESTIONS:
1. For each position of the target sphere, compare the resultant of the sum of the final momentum of the target sphere and the incident sphere with the original momentum of the incident sphere. Explain your findings.
2. For each trial, measure the angle formed between the two final momentum vectors. Can you make any generalizations?
PRE LAB DISCUSSION: If no net force acts upon a moving object, it will travel in a straight line with no change in speed. To cause an object to travel in a circular path, a force constantly p act upon the object. This force is called the centripetal force and therefore will always be directed toward the center of the circle.
PURPOSE: To determine the relationship between velocity and the centripetal force.
MATERIALS:
glass tube (10-20 cm) string (about 1.5 m) rubber stopper (2-hole)
washers stopwatch alligator clip
PROCEDURES:
1.Make a data table with headings like the one below and include it in the "Observations and Data" section of your lab report.
|
Force (# of washers) |
Time for 30 revolutions |
2. Tie the rubber stopper to one end of the nylon cord. in your hand about 50 cm from the stopper, try whirling it above your head in a circular path. As you whirl it faster, what happens to the force needed to keep the string from sliding through your fingers? Let your lab partners try this. Record your observations.
3.Pass the free end of the string through the glass tube and attach the paper clip at that end. Bend the paper clip so that it well support the metal washers. Hang five washers at the cord. Adjust the cord so that the radius of the circular path of the stopper will be about 80 cm to the middle of the stopper. Mark this by attaching an alligator clip to the string where it emerges from the bottom of the tube. Measure the distance from the top of the tube to the middle of the stopper. Record this measurement.
4.Practice whirling the stopper in a circular horizontal path above your head. It is important that the tube move as little as possible. T traveling at the desired speed when the weight of the centripetal force needed for the stopper to maintain its circular path of 80 cm. The in of the alligator clip clip should stay just a little below the glass tube. If the alligator clip be, you are whirling the stopper too rapidly. If the clip starts to descend, you are whirling the stopper too slowly.
5.When the stopper is moving with the desired rotational speed, have your lab partner use the stopwatch to measure the time it takes the stopper to complete 30 revolutions.
6.Add five more washers and repeat step 5. Repeat this procedure three more times, each time adding five washers until the total weight is 25 washers.
ANALYSIS:
1.Calculate the circumference of the circle that the stopper travels in.
2.Make a table like the one below and perform the calculations required to fill it in. Be sure to show the setups for all calculations on your calculation page. You may include the table in the "observations and data" section of your lab report.
|
Force (# of washers) |
Time for 1 revolution |
Speed (m/sec) |
Speed2 (m/sec)2 |
3.In this investigation, you varied the force (number of washers) in each trial. Therefore force is the independent variable and should go on the x-axis. However, in this investigation plot force on the vertical axis and speed on the horizontal axis. Draw the line or smooth curve that best fits your points.
4. On another graph, plot force on the vertical axis and speed squared on the horizontal axis. Draw the line or smooth curve that best fits your points.
CONCLUSIONS AND QUESTIONS:
1.What according to the first graph, is there a direct relationship between centripetal force and speed?
2. What does the second graph tell about the relationship between centripetal force and speed squared?
3. Find the equation for centripetal force in your text. Do the results of this investigation support the equation? Explain.
PRE LAB DISCUSSION: Kepler's laws deal with the motion of planets as they orbit the sun. As it turns out these laws are true for any orbital system (like the earth and moon). The laws deal with the shape of the orbit as well as the speed of the orbiting body.
PURPOSE: To draw the orbit of a planet (an ellipse) and demonstrate how the force and velocity varies as the planet orbits.
MATERIALS:
2 thumbtacks cardboard sheet of paper string (30 cm) pencil
PROCEDURES:
1. Place the paper on the cardboard and push the thumbtacks into the paper so that they are between 7 - 10 cm apart.
2. Make a loop with the string. Place the loop over the two thumbtacks. Place the pencil in the loop and pull it away from the tacks until the string is tight. Keeping the string tight move the pencil around in a circle-like motion until you have a complete ellipse.
3. Remove the tacks and string. Draw a small star centered on one of the holes from the thumb tack.
ANALYSIS:
1. Draw the position of the planet in the orbit where it is farthest from the star.
2. Measure the distance from this position to the center of the star and record it.
3. Draw a 1 cm long force vector from the planet directly toward the star. Label this vector 1.0 F.
4.Draw the position of the planet in the orbit where it is nearest from the star.
5. Measure the distance from this position to the center of the star and record it.
6. Calculate the amount of force on the planet at the closest distance. Remember that gravity is an inverse square force.
7. Draw a vector of the correct length from this position.
8. Draw the planet at two other positions on the orbit and repeat steps 6 and 7 for each position.
CONCLUSIONS AND QUESTIONS:
1.Assume the planet moves in a clockwise pattern on the ellipse. Draw a velocity vector at each planet position to show the direction and relative magnitude of the planet's velocity. Remember to refer to Kepler's Laws when doing this.
2.Look at the velocity and force vectors on your diagram. Identify on your diagram the part of the orbit where the planet is gaining speed and where it is losing speed.
PRE LAB DISCUSSION: The simple pendulum consists of a mass called the pendulum bob suspended from a support by a thread. A complete vibration of a pendulum consists of one swing over and one swing back. The time for a complete vibration is called the period (T) of the pendulum. This is usually measured in seconds. When a pendulum swings through a small arc, its bob is undergoing simple harmonic motion.
PURPOSE: To test the effect of certain variables on the period of a pendulum.
To describe the relationship between period and length of a pendulum.
MATERIALS:
pendulum support thread meter stick stopwatch
pendulum bobs (of different mass) lab balance
PROCEDURES:
1.Measure and record the mass of the two pendulum bobs.
2.Suspend the two pendulum bobs side by side. Make each pendulum the same length (50 cm as measured from the point of support to the center of each bob).
3.Using a ruler, pull the bobs aside together to the same height (about 10° or 15°) so that they will swing together through the same height. Release the bobs simultaneously by quickly dropping the ruler. Observe the two bobs of different mass as they swing through their arcs. Record your observations.
4.Start the bobs swinging simultaneously again, but this time release each from a different height. Try this again, this time switch the bob that is released from the greater height.Do they swing through different arcs at the same or different times? Record your observations.
5. Remove one of the pendula. Vary the length of the remaining pendulum by grasping the thread at different distances from the bob and allowing the bob to swing through several vibrations. Record your observations.
6.To be more quantitative, use your stopwatch to measure the time required to for the pendula of different lengths to swing through 40 complete vibrations. Make a table like the one below, then begin your measurements with the 50 cm pendulum. Vary the length of the pendulum in increments of 10 cm and collect data for pendula that range from 10 cm - 80 cm.
ANALYSIS:
1.Calculate the period of the pendulum for each length. Record the results of your calculations in a neat table.
2.Plot the period (T) on the vertical axis and the corresponding length on the horizontal axis.
3.Calculate the period squared (T2) of the pendulum for each length. Record the results of your calculations in a neat table.
4.Plot the period squared (T2) on the vertical axis and the corresponding length on the horizontal axis.
CONCLUSIONS AND QUESTIONS:
1.What do your observations of procedure 3 indicate about the relationship between the mass of the bob and the period of a pendulum?
2.What do your observations of procedure 4 indicate about the relationship between arc of swing and the pendulum period?
3.What do your observations of procedure 5 indicate about the relationship between length of a pendulum and its period?
4. Compare the graphs, what relationships do they indicate?
5.Using your second graph, determine the length of a pendulum that would have a period of 1.0 sec. Construct such a pendulum. Time it as it swings through 60 vibrations. How well does your prediction agree with the results?
PRE LAB DISCUSSION: As you walk up a set of stairs, work is done against gravity. That is a certain force, in this case your weight, is moved a certain distance (the height of the stairs). In order to do this work it requires energy. You use up a certain amount of energy when you walk up the stairs, which is equal to the work done. Some people use this energy rapidly, others who may have the same weight, may walk up the stairs slowly and use the energy at a lower rate. Power is a measure of how fast energy is used, or the rate at which work is done.
PURPOSE: To determine the amount of work and power it takes to walk up a set of stairs.
MATERIALS:
meter stick metric bathroom scale stopwatch
PROCEDURES:
1. Measure the vertical height of the stairs.
2. One member of the lab group should approach the stairs at a steady speed without running.
3. The timer should start the stopwatch when the climber hits the first stair and stop the clock when the climber reaches the top.
4. Repeat procedures 2 and 3 until all group members have climbed the stairs.
ANALYSIS:
1. Calculate your own work and power.
2. Compare your work and power to the work and power of the members of your group and others in the class.
CONCLUSIONS AND QUESTIONS:
1. Which students did the most work? Explain.
2. Which students had the most power. Explain with examples.
3. Calculate your power in kilowatts.
4. Suppose your local electric company charges 8¢ per kilowatt hour. If you walked up the steps continuously for one hour, how much money would this climb be worth?
5. How long would a 60 watt bulb have to burn to use the same amount of electrical energy?
PRE LAB DISCUSSION: This is one of the seven labs required by New York State. In it you will investigate the relationship between the length of stretch of a spring and the applied force.
When a force is applied to an object, the object may be stretched, compressed, bent, or twisted. These deformations occur while the force acts on the object. Within limits, when the force no longer acts, the object returns to its original shape.
PURPOSE: To determine the relationship between the length of stretch of a spring and the applied force.
GENERAL DIRECTIONS:
Working with a partner:
1. Devise a procedure to accomplish the purpose above.
2. Compile a list of materials that you will need to complete your lab investigation.
3. Have your instructor check your procedures.
4. After having had your procedures approved, carry out your investigation.
5. Compile your data in a table.
6. Graph your data, being careful to plot the dependent and independent variables on the correct axis.
7. Answer the questions below.
8. Prepare a written report inlcuding: Purpose, Procedure, Data (include your data table and your graph., Calculations, Conclusions (use the answers to the questions below), and a Discussion.
CONCLUSIONS AND QUESTIONS:
1. What kind of a relationship between the stretch of a spring and applied force does the graph of the data indicate?
2. The spring constant is defined as the slope of an enongation vs force graph. Calculate the spring constant for your spring.
3. Using your graph, pridict the elongation of the spring for three forces that you did not apply to it. List both the force and the elongation.
4. The pointer on a spring scale moves 2.0cm when a force of 9.8N is added to it. How many cm will a 45N force cause the pointer to move?
5. Determine the spring constant for the spring in question #4.
PRE-LAB DISCUSSION When a car sits atop a hill it has potential energy with respect to the bottom of the hill. As it rolls down the hill, it loses potential energy, but gains kinetic energy. There should be a relationship between the amount of potential energy it loses and the amount of kinetic energy it gains.
PURPOSE To compare the starting potential energy of a cart on top of a ramp to the kinetic energy it has gained when it reaches the bottom of the ramp.
GENERAL DIRECTIONS
1. Read the "Pre-Lab Discussion" and "Purpose" above.
2. Think about what procedures you will need to use in order to solve the problem.
3. Using the brainstorming techniques we used on previous labs, develop a procedure that you think may be used to solve the problems.
4. Share your ideas with your lab partners, and as a group devise a procedure that you think will work. Select a recorder to write these procedures.
5. Check with members of other groups and using their ideas further refine your procedures.
6. Submit your procedures to your teacher for approval.
7. Carry out your approved procedures and collect the data in neat clearly labeled tables.
8. A you collect your data, observe the motion of the cart as it rolls down the ramp. Describe this motion in a full sentence in the "observations and data" section of your lab report.
9. Carry out the calculations in the "analysis" section below and include them on your calculation page.
10. Answer the questions in the "conclusion and questions" section below and include the answers in your lab report.
ANALYSIS
1. On your Calculation section calculate the KE and PE of the cart.
CONCLUSIONS AND QUESTIONS
1. Compare the starting potential energy to the kinetic energy at the bottom of the hill. Should the values be equal? Explain any differences.
2. Could the starting potential energy be less than the measured kinetic energy? Explain.
3. Does the angle of the ramp affect the potential energy? Explain your reasoning.
PRE-LAB DISCUSSION A calorimeter is an apparatus designed to prevent the objects placed in it form gaining or losing thermal eneergy to the surroundings. A substance placed in the calorimeter will maintain its temperature at a constant level for an appreciable length of time. To thd calorimeter cup of known mass, containing a measured mass of cold water, yuou will add a measured mass of warm water. Heat will pass from the warm water to the cold water andcalorimetter cup until the whole system is at the same temperature. You will then determine the amount of heat supplied by the warm water and the amount of heat absorbed by both the cold waterand the calorimeeter cup. Youo will then determine the amount of heat supplied by the warm water and the amount of heat absorbed by the cold water and the calorimeter cup.
PURPOSE
To compare the amount of heat transferred from one object to another.
MATERIALS
calorimeter thermometer lab balance large beakers
PROCEDURES
1. Determine the mass of the inner calorimeter cup. and record it. Fill the cup nearly half full of cold water. Determine the mass of the cup and the cold water and record it.
2. Assemble calorimeter.Measure the temperature of the cold water. Assume that the temperature of the cup is the same as the temperature of the cold water. Record the initial temperature of the cold water and the cup.
3.Warm some water in a beaker to a temperature of about 80°C. Measure and record the initial temperature of the hot water. IMMEDIATLELY add some of the hot water to the calorimeter cup until it is nearly full. Replace the cover at once.
4. Stir the mixture gently with the thermnometeruntil a constant temperatue is reached. Observe the thermometer closely because the temperature change will not be large. Record this final temperature of the hot water, cold water and calorimeter cup.
5. Measure and record the mass of the cup and all the water added to it.
ANALYSIS
1. Determine the mass of the cold water.
2. Determine the mass of the hot water.
3. Determine how much heat was gained by the cup (assume that it is made of aluminum).
4. Determine how much heat was gained by the cold water.
5. Determine the total amount of heat gained.
6. Determine how much heat was lost by the hot water.
CONCLUSIONS AND QUESTIONS
1.How well does the amount of heat gained by the system compare to the amount of heat lost? Account for any differences.
PRE-LAB DISCUSSION
The wave characteristics that you will observe at this time are common to all waves. There are not separate characteristics for sound waves, light waves, water waves, and other kinds of waves. In general, all waves in a coiled spring to learn about waves in general. To do this in an orderly manner, each characteristic will be outlined clearly in the procedure along with any instructions you might need in order to observe them.
PURPOSE
To observe and describe some basic wave characteristics.
MATERIALS
slinky coil spring thread stopwatch
PROCEDURES
Record your observations of EACH of the following procedures on a separate sheet of paper. Include them in your "Observations and Data" section of your lab report.
A. Transverse and Longitudinal Waves
1. Have your lab partner hold one end of the slinky and stretch it along a smooth floor until it is about 10 m long. Practice shaking your end of the spring sideways until you are able to send a clear pulse along its length. Several pulses together will form a transverse wave train. Record the direction in which the pulses travel and the direction n which the coils of the spring move.
2. Reach a short distance down the spring's length and gather the coils toward you and then quickly release them. The pulse that travels along the spring is a longitudinal pulse. Record the direction in which the pulses travel and the direction n which the coils of the spring move.
B. The Speed of All Waves of the Same Kind in a Given Medium
1. Generate a transverse pulse in the coil. Keep the stretch of the coil constant. Estimate the speed of the pulse in the medium. Generate a second pulse but make it larger or smaller than the previous pulse. Compare the speeds of the pulses, record your observations. If you are undecided, you might try timing the pulse with the stopwatch. Try to generate waves of different amplitudes and frequencies. Compare the speeds of the waves and record your observations.
C. Wavelength and Frequency
1. Shake the spring back and forth rapidly to generate wave trains in the spring. The wavelength of a wave in the spring is the distance from a crest on one side of the spring to the next crest on the same side. The frequency of the wave is the same as the frequency at which you shake the spring. Try shaking the spring regularly but slowly and then regularly but rapidly. Observe the wavelengths of the waves and record your observations.
D. The Interference of Waves
1. Have your partner grasp one end of the spring while you grasp the other end. Practice sending pulses toward each other at the same time. Try this and closely observe the pulses when they come together and also after they pass through one another. Try pulses of the same and different shapes. Send equal pulses toward each other with both partners initially displacing the spring to their rights. Now try the same experiment with one partner displacing the spring to the right while the other partner displaces it to the left. Record your observations of these two procedures.
E. Reflected Waves
1. Have your partner hold one end of the spring very firmly. Send a transverse pulse to the rigid end and observe the phase of the reflected pulse compared to the phase of the original pulse. Record your observations.
2. Now tie a long thread to one one of the spring. Have your partner hold the thread while you send a pulse toward the end supported by the string. (The thread represents a less rigid medium than the one in which the wave has been traveling.) Observe the phase of the reflected pulse, record your observations.
F. Transmitted Waves
1. Connect the slinky with the other coil spring. consider the spring and the slinky as two different media. Stretch the slinky as before. Have your partner hold the end of the spring and you hold the end of the slinky. Try sending pulses and shout waves down each spring. Observe their behavior at the boundary between the two springs, record your observations. Observe how a wave changes as it passes from one medium into the other, record your observations.
CONCLUSIONS AND QUESTIONS
1. How well do your observations in section B and C support the wave equation in which v=ƒl?
2. Summarize the major characteristics of wave motion that you observed in this investigation.For Questions 3-5 sketch the results of wave a and wave b
a. when they meet b. when they pass each other
PRE-LAB DISCUSSION
The speed of all waves is given by the relationship:
where v is the speed of the wave in the medium, f is the frequency of the wave, and l is the wavelength of the wave. The frequency of a wave is necessarily the same as the frequency of the vibration generating the wave. Sound waves created by a tuning fork vibrating at 256 vibrations per second have a frequency of 256 hertz (cycles per second).
Using the principle of resonance, the wavelength of sound waves will be determined. If a vibration tuning fork having the same natural frequency as an air column is held above the air column, the vibrating fork will push the air column at just the right frequency to start the air column vibrating. this is called resonance. The vibration of the air column will increase in amplitude with each vibration of the fork. The sound waves from the vibrating column of air will become much louder than the sound from the tuning fork. thus, sound waves from the tuning fork are reinforced by sound waves from the air column. for a tube closed at one end, resonance occurs when the length of the tube is approximately one-fourth the length of the sound waves being reinforced.
PURPOSE:
To determine the wavelengths of sound waves of known frequencies and use them to calculate the speed of sound in air.
MATERIALS:
resonance cylinder apparatus
meter stick
tuning forks (3)
glass marking pencil
PROCEDURE:
1. Measure and record the diameter of the resonance tube and the room temperature.
2. Make a data table with the following headings:
Frequency (Hz), Length of air column (cm)
3. Add water to the glass cylinder until it is full, hold the bottom of the beaker level with the top of the cylinder. If the water level in the cylinder drops because of it filling the tubing, refill the cylinder. By raising and lowering the beaker, the water level in the cylinder can be controlled.
4. Strike the tuning fork with the rubber hammer. Hold the vibrating tuning fork horizontally as close to the open end of the tube as possible. Lower the beaker so that the water level in the cylinder drops. Stop when the sound is best reinforced and mark the outside of the tube showing the water level in the cylinder.
5. Measure the distance from the top of the cylinder to the water level. Record this distance in your data table along with the frequency of the tuning fork that was used in this trial.
6. Repeat this process with at least two different tuning forks.
7. After having found the shortest cylinder length that produces sound reinforcement, again move the water level down until reinforcement occurs again. Record your observations. Do this for one tuning fork only.
ANALYSIS/CALCULATION:
1. The length of the air column must be increased by four-tenths of the diameter of the tube (0.4d) to correct for the small amount of air just outside the top of the cylinder that vibrates with the air column in the cylinder. Calculate 0.4d and add this to the length (L) of the column to get the "corrected length" (CL). ( CL = L+ 0.4d )
2. Since resonance occurs at one-fourth the wavelength multiply each of the corrected lengths by 4 to get the wavelength of each sound wave produced.
3. Using the formula in the pre-lab discussion, calculate the speed of each sound wave produced.
4. Find the average of the speeds and put a plus/minus value on it. This is the experimental value of the speed of sound in air.
CONCLUSIONS AND QUESTIONS:
1. The speed of sound in air is 332 m/sec at 0°C. it increases at 0.60 m/sec for each Celsius degree above zero. Calculate the speed of sound at the temperature of the laboratory.
2. Find the absolute and percent difference between your value o f the speed of sound in calculation 4 and the value given by question 1 above.
3. In Procedure Step 7, were there any other lengths that produced reinforcement? If so what wavelength do they represent?
4. Sound waves travel in water at about four times their speed in air. When sound waves leave air and enter water, the equation v=fl tells us hat since v increases, either f or l or both must increase. From experiments with springs which variable(s) changes?
5. An observe sees a lightning flash from a distant thunderstorm and 12 seconds later hears the sound. If the temperature of the air is 20°C, how far from the storm is the observer? (Assume the time it takes for the light to travel is negligible.)
PRE-LAB DISCUSSION
When light rays are reflected from surfaces, the rays are found to be reflected in such a way that there is a relationship between the angle of reflection and the angle of incidence. The relationship is known as the law of reflection. both angles are measured from the ray to an imaginary line perpendicular to the surface at the point where the ray is reflected. This perpendicular line is called the normal.
PURPOSE
To determine the relationship between the angle of incidence and the angle of reflection.
To locate the image of an object in a plane mirror, and to describe the characteristics of the object.
MATERIALS
plane mirror straight pins metric ruler modeling clay
protractor cardboard blank sheet of paper
PROCEDURES
A. Locating the Image Position
1. Place a sheet of copy machine paper on the piece of cardboard. Draw a line ML (mirror line) across the middle of the paper (short way). Support the mirror vertically by using the modeling clay. Center the silvered edge of the mirror (back surface) along the mirror line, ML.
2. About 4 cm in front of the mirror, make a dot on the paper with a pencil and label it point P. Place a pin upright in point P.
3. Lower your head so that your eyes are level with the top of the paper. Place your ruler on the paper about 5 cm to the left of the pin. Sight along the ruler so that the edge of the ruler is lined up on the image, draw a line along it. Label this line A.
4. Move the ruler another 3 or 4 cm to the left and sight it at the image of the pin once more. Draw a line along the edge of the ruler. Label this line B.
5. Remove the pin and mirror from the paper. Extend lines A and B to the line ML. Using dotted lines, extend each of the lines beyond the mirror position until they intersect. This is the position of the image I in the mirror. Measure the perpendicular distance from P to ML and from I to ML. Record the distances in the data section of your lab report.
B. The Law of Reflection
1. Label the point where line A meets line ML point X. Draw a line from P to point X. Using your protractor construct a line perpendicular to ML at point X. This line is the normal, label it N. Measure the angle of reflection (AXN) and the angle of incidence (PXN). Record the measures of these angles in the data section of your lab report. Label the point where line B meets line ML point Y. Draw a line from P to point Y. Using your protractor construct a line perpendicular to ML at point Y, label it N'. Measure the angle of reflection (BYN') and the angle of incidence (PYN'). Record the measures of these angles in the data section of your lab report.
C. Image Orientation
1. Set up the mirror once more on a line drawn across the center of a fresh piece of paper. Draw a triangle in front of the mirror and label the vertices A, B, and C.
2. Place the pin in vertex A. Site along the ruler to obtain two lines from the image of the pin at A, as you did in steps A3,4. Label the lines A1 and A2.
3. Remove the pin from A and place it in vertex B. Sight two lines and label them B1 and B2.
4. Place the pin in Vertex C and repeat the procedure.
5. Remove the pin and the mirror. Locate the image of point A as you located the image of point P in step A5. Label the image A'. Do the same for the images of points B and C, labeling them B' and C' respectively.
6. Construct the image of the triangle. If your constructed image of the triangle did not resemble the original triangle closely, get another sheet of paper and try part C again.
7. Measure and record in a neat data table the distances from each of the six points to the mirror line (ML).
CONCLUSIONS AND QUESTIONS
1. From your observations, does a relationship seem to exist between angle of incidence and angle of reflection? If so what is it?
2. A ray of light is incident upon a mirror at an angle of 30°. What is the angle between the incident ray and the reflected ray?
3. How far behind the mirror is the image of an object that is located 50 cm in front of a plane mirror?
4. Compare the size of your original triangle in Pat B with the size of your constructed image of the triangle.
5. Why do you think the image produced by a plane mirror is called a virtual image?
PRE-LAB DISCUSSION
Recall from the last lab that the normal is a line drawn perpendicular to the surface at the point at which a ray strikes it, and that the angle of incidence is the angle between the ray and the normal (i). If a ray passing through air strikes a surface and is not reflected, but transmitted, it will slow down. If the angle of incidence is anything other than zero (an "oblique" angle), the light ray will bend as it passes into the second medium. This phenomenon is called refraction and the ray that passes into the medium is called the refracted ray. By extending the normal into the second medium, the angle between the normal and refracted ray may be measured, the angle is called the angle of refraction. (r).
The ratio of the speed of light in a vacuum (or air), to the speed of light in a medium is called the index of refraction of the medium. In other words light travels slowest in materials with a high index of refraction. In 1621, the Dutch mathematician Willebrord van Roijen Snell discovered a relationship between the index of refraction of a medium and the angles of refraction and incidence known as Snell's Law.
PURPOSE
To measure the angles of incidence and refraction of a light ray incident on a glass plate.
To determine Snell's Law.
MATERIALS
|
rectangular glass plate |
protractor |
|
metric ruler |
plain white paper , 2 pc. |
|
lab balance |
PROCEDURES (Refer to the diagram below)
1. Place the rectangular glass plate on the center of a sheet of white paper. Trace the outline of the plate in pencil.
2. Remove the glass plate and construct a normal NB at the top left of the outline.
3. Using your ruler and protractor, draw a heavy line AB at an angle of 30° with the normal. Angle ABN is the angle of incidence (angle i)
4. Replace the glass plate over the outline on the paper. With your eyes on a level with the glass plate, sight along the edge of the glass plate opposite the line AB until you locate the line through the glass. Sight your ruler at the line until its edge appears to be a continuation of the line. Draw the line CD.
5. Remove the glass plate and draw another line connecting lines CD and AB. Extend the normal NB to the other side of the line. Label it N'.
6. Measure angle CBN'. This is the angle of refraction (angle r).
7. Make a table with headings like the one below. Look up the sines corresponding to each angle and enter them in the table.
|
|
|
|
|
8. Use the second sheet of paper (or use the other side to conserve paper) and repeat steps 1-6 using an angle of incidence of 45°. Record your results in the table.
9. Use the ruler and balance to make the necessary measurements to determine the density of the glass block in grams/cm3 (recall that Density = mass/volume). Record your measurements in a neat table.
ANALYSIS/CONCLUSIONS AND QUESTIONS:
1. Glass scientists use the rule that index of refraction of glass is 1.00 less than the value of the density (n=d-1.00). Calculate the density of the glass, then calculate the expected index of refraction (index of refraction has no units). Use this as the accepted index of refraction for the glass block.
2. For each angle divide sin i by sin r. Take the average of the two and come up error limits on your answer. How does the value you get compare to the index of refraction of glass?
3. What is the index of refraction of a material in terms of sin i and sin r?
4. According to your diagrams, are light rays refracted away from or towards the normal as they pass obliquely from a less optically dense medium, like air, into a more optically dense medium like glass? Which way do they bend when they leave the glass and enter the air.
5. The speed of light in air is close to 3 x 108 m/sec. Calculate the speed of light in glass.
PRE-LAB DISCUSSION
In the last lab you found that light rays bend as they pass through an optically dense medium. A lens is a device that uses refraction to produce an image of an object by bending light rays that pass through it.
A convex or converging lens is thicker in the middle of the lens than at the edge of the lens. The shape of the lens bends light in such a way that parallel rays will converge at a point on the other side of the lens, thus the name "converging lens". The point at which the rays converge is the focal point (F) of the lens, and the distance from the lens to the focal point is called the focal length. Different lenses have different focal lengths because of their shapes.
An imaginary line drawn perpendicular to the lens is called the principal axis. When light rays strike the lens perpendicular to the principal axis, they will converge on the other side of the lens at the principle focus . The principle focus, always lies on the principle axis. Another important position is twice the focal length designated by 2F. Since light rays may pass through the lens in either direction, F and 2F exist on either side of the lens.
PURPOSE
To observe the positions and characteristics of images produced by convex lenses.
MATERIALS
double convex lens optics bench (meter stick, supports, candle and holder, lens holder, screen and holder)
PROCEDURES (Refer to the diagram above)
Part A: Locating the Focal Point
1. Attach the supports (legs) to the meter stick. Place the meter stick on the lab bench so that the 0 cm end is closest to the windows.
2. Carefully clip the lens to the holder, and place the lens and holder at about the 50 cm mark on the meter stick.
3. Attach the screen to the holder and place screen and holder on the meter stick someplace between the 50 and 100 cm marks on the meter stick (the side of the meter stick farthest from the windows).
4. Partially open one of the window shades. Move the screen and support back an forth on the meter stick until a clear image of the windows is obtained. Since the windows are at a large distance from the lens, the distance between the lens and the screen is, very close to, and may be considered to be, the focal length of the lens. Record this distance.
Part B: Characteristics of Real Images
In this section you will find the characteristics of the images produced by the lens as the location of the object in front of the lens changes. As you make your observations for each location of the object answer each of the following questions.
- Image Position: Where is the image located in terms of F, 2F, and the lens?
- Type of Image: What type of image is it, real or virtual? (Only real images can be projected on a screen.)
- Image Size: Is the image smaller or larger than the object?
- Direction of Image: Is the image inverted (upside down and backward) or erect (same orientation as object)?
When you finish the procedures, organize your observations into a neat table.
5. Close the shades and place the candle in the support and put it on the meter stick on the side of the lens opposite the screen.
6. Position the candle at some point beyond 2F and light it. Move the screen back and forth until an image is produced on it. Record your observations as outlined above.
7. Repeat procedure 6 with the candle at the following locations: at 2F, between F and 2F.
Part C: Characteristics of Virtual Images
8. Place the candle between F and the lens. Try moving the screen around to get an image. Now look through the lens at the candle. What you see is a virtual image. Answer the above questions for the candle at this position. Include your findings on your data table.
ANALYSIS/CONCLUSIONS AND QUESTIONS:
1. For each object location (beyond 2F, at 2F, between F and 2F, between F and the lens), draw a ray diagram to illustrate how the image was formed.
2. Compare and contrast real and virtual images.
PRE-LAB DISCUSSION
Objects can acquire static electric charges by either gaining or losing electrons. An object that gains electrons has a net negative charge, an object that loses electrons has a net positive charge. Any object can acquire a static charge, however, only those objects separated from the ground by an insulator (nonconductor) can retain their charge for any length of time.
When completing this investigation keep in mind these three rules:
1. Electrons move easily, both within an object and from one object to another.
2. Rubber rods, when rubbed with wool or fur obtain electrons from the fur and become negatively charged.
3. Glass rods, when rubbed with silk, lose electrons to the silk and become positively charged.
PURPOSE
To determine the behavior of static charges.
MATERIALS
pith ball suspended by a silk thread electroscope
rabbit fur silk pad
rubber rod glass rod
PROCEDURES
For each section, record your observations as directed.
Part A: Charging a Pith Ball
1. Rub the rubber rod with fur. Then bring the rod close to a suspended pith ball. Observe carefully and record the sequence of events.
Part B: Charging the Electroscope by Conduction
2. Charge the rubber rod by rubbing it with fur. Touch the rubber rod to the top of the electroscope. Record your observations.
3. Touch the top of the electroscope with your finger. Record your observations.
4. Charge the glass rod positively by rubbing it with silk. Touch the glass rod to the top of the electroscope. Record your observations.
5. Touch the top of the electroscope with your finger. Record your observations.
Part C: Testing the Charge of An Object.
6. Charge the rubber rod with fur and touch the electroscope. The electroscope is negatively charged by the conduction of electrons from the rod to the electroscope.
7. Charge the glass rod positively by rubbing it with silk. Bring it near the charged electroscope from Step 6. Touch the top of the electroscope with your finger. Record your observations.
8. Recharge the electroscope with the rubber rod. Bring the negatively charged rubber rod near the charged electroscope. Touch the top of the electroscope with your finger. Record your observations.
Part D: Charging the Electroscope by Induction.
9. Ground the electroscope by touching it with your finger. Bring a negatively charged rod near but not touching the electroscope. Record your observations.
10. Remove the rod. Record your observations.
11. Again bring the charged rod near the electroscope. With the rod still close, quickly touch your finger to the electroscope and remove it, all the while, holding the charged rod near the electroscope. Record your observations.
12. Now remove the charged rod. Record your observations.
13. Using the method in Part C, test the charge on the electroscope.
CONCLUSIONS AND QUESTIONS:
1. Explain the action of the glass rod and the pith ball.
2. How do like charges and unlike charges interact?
3. Explain what happens in the electroscope, in terms of electrons, when a charged rubber rod is brought close to it. Explain what happens in the electroscope, in terms of electrons, when a charged glass rod is brought close to it.
4. Explain what happens in the electroscope, in terms of electrons, in procedures 4 and 5.
5. Compared to the charging body, what is the charge on an electroscope when it is charged by....
...conduction?
...induction?
PRE-LAB DISCUSSION
As the potential applied across a conductor changes there should be an observable change in the current running through the circuit.
PURPOSE
To determine the relationship between the current and potential difference in a simple circuit.
MATERIALS
lab volt power supply test leads
voltmeter ammeter
knife switch
resister of known resistance resister of unknown resistance
PROCEDURES A
Before beginning, make a data table with headings like the one below:
|
Potential Difference (volts) |
Current (amps) |
1. Record the printed value of the Resister.
2. Set up the circuit as shown in figure I. Important: Have the teacher check your setup before proceeding any further.
3. Turn the adjustment knob on the lab volt all the way in the counter-clockwise direction.
4. Close the knife switch and slowly turn the adjustment in a clockwise direction until the voltmeter reads one volt.
5. Quickly read the value on the ammeter and record your readings in the data table . Open the knife switch as soon as possible after reading the ammeter.
6. Repeat steps 4 and 5 increasing the voltage in one volt increments until a total of 6.0 volts is reached.
Fig 1.
ANALYSIS A
1. Plot Potential Difference vs. Current with Potential Difference on the y-axis. What type of relationship does the graph indicate? Explain.
2. Calculate the slope of the graph. Compare the value you get for slope with the value of the resister that you used. How does resistance relate to your graph?
3. Write the mathematical relationship between resistance, current and potential difference that your data seems to indicate.
PROCEDURES B
1. Use what you learned in procedure A to determine the resistance of one of the unknown resistors.
ANALYSIS B
1. Include any graphs or calculations required to determine the resistance in your lab report.
CONCLUSIONS AND QUESTIONS:
1. State Ohm's Law both mathematically and in words.
2. Describe the placement of an ammeter within a circuit.
3. Describe the placement of a voltmeter within a circuit.
4. Solve each of the following:
a. A 60-watt bulb has a voltage of 120 volts applied across it and a current f 0.5 amps flows though the bulb. What is the resistance of the bulb?
b. A resistor of 60.0 ohms has a 0.4 amp current flowing through it when connected to a battery. What is the voltage of the battery?
c. The resistance of a small electric motor is 24 ohms. If the motor operates on 6.0 volts, what current does the motor require?
PRE-LAB DISCUSSION
There are two basic types of circuits or paths through which electrons can travel, series and parallel circuits. In series circuits resistors are connected with the voltage source in such a way that the total current must flow through each resistor in turn. The effective resistance of a series circuit is the sum of the resistances of the individual resistors in the circuit.
Reff = R1 + R2 + R3 + .....
Other calculations are based on Ohm's Law
I = V/R
When resistors are connected in parallel, each resistor provides a path for the electrons to follow and, therefore, reduces the effective resistance to the current. The effective resistance of parallel resistors can be found mathematically by applying the equation.
1/Reff = 1/R1 + 1/R2 + 1/R3 + .....
It will be necessary for you to follow the circuit diagrams very closely. Although the diagrams show several meters in use at once, you have been provided with only two meters. Therefore, you must move the meters from position to position until all readings are obtained.
PURPOSE
To apply Ohm's law to a series circuit then to a parallel circuit.
MATERIALS
D.C. power supply or dry cells
Three resistors 5½-30½ (no more than two resistors should have the same value)
Connecting wires
Knife switch
Voltmeter (0-15 volt)
Ammeter (0-15 amp)
PROCEDURE A: Series Circuit
Open the switch as soon as the readings are made!
1. Arrange three resistors in series with each other. Connect the resistors in series with the ammeter (AT), open switch, and voltage source. Connect the voltmeter in parallel with the voltage source (VT), as in the diagram. Set the voltage at about 6 volts.
2. Close the switch long enough to read AT and VT record your readings. Quickly open the switch.
3. Move the ammeter to position A1. Repeat step 2. Move the ammeter to positions A2 and A3, repeating step 2 each time.
4. With the three resistors still in series, use the voltmeter to find the voltage drop across each resistor. Touch the lead wires of the voltmeter to each end of resistor R1, close the switch, and read the meter, record your readings. Quickly open the switch.
5. Repeat Step 4 for R2 and R3.
PROCEDURE B: Parallel Circuit
6. Arrange three resistors in parallel with each other. Connect the resistors in series with the ammeter (AT), open switch, and voltage source. Connect the voltmeter in parallel with the voltage source (VT), as in the diagram. Set the voltage at about 6 volts.
7. Repeat steps 2 and 3 from procedure A.
8. With the three resistors still in parallel, use the voltmeter to find the voltage drop across each resistor. Touch the lead wires of the voltmeter to each end of resistor R1, close the switch, and read the meter, record your readings. Quickly open the switch.
9. Repeat Step 8 for R2 and R3.
PROCEDURE C: Qualitative Observations
10. Remove everything from the circuit except the switch. Set the voltage to 3.0 volts. DO NOT CARRY OUT THE FOLLOWING PROCEDURES WITH VOLTAGES GREATER THAN 3.0 VOLTS. Damage to the equipment may occurr if higher potential differences are used.
11. Build a circuit using one light bulb, the power supply and the switch. Close the switch, reset the voltage to make sure that it is at 3.0 volts. Record your observations.
12. Open the switch and add another light bulb in series, close the switch. How does the brightness of the bulbs compare to the brightness of the bulb in the original circuit? Open the switch. Record your observations.
13. Add a third bulb in series. Close the switch. Compare the brightness of the bulbs now to their brightness in the procedures above. Record your observations. Unscrew and remove one of the bulbs, what happens? Open the switch. Record your observations.
14. Remove the bulbs added in procedures 12 and 13. Add a second bulb in parallel. Close the switch. How does the brightness of the bulbs compare to the brightness of the bulb in the original circuit? Open the switch. Record your observations.
15. Add a third bulb in parallel. Close the switch. Compare the brightness of the bulbs now to their brightness in the procedures above. Record your observations. Unscrew and remove one of the bulbs, what happens? Unscrew and remove another one of the bulbs, what happens? Open the switch. Record your observations.
ANALYSIS A : Series Circuits
1. Use Ohm's Law and the values you obtained for AT and VT to calculate the total resistance of the circuit.
2. Add the printed values of the resistors together.
ANALYSIS B: Parallel Circuits
3. Use Ohm's Law and the values you obtained for AT and VT to calculate the total resistance of the circuit.
CONCLUSIONS AND QUESTIONS:
1. How do the values you obtained in Analysis 1 and 2 compare? What generalization can you make about the total resistance in a series circuit.
2. a. Compare all the ammeter readings in the series circuit, what generalization can you make? Do the same with the voltmeter readings in the series circuit.
b. Compare all the ammeter readings in the parallel circuit, what generalization can you make? Do the same with the voltmeter readings in the series circuit.
3. Consider the result you obtained for Analysis 3 and the values of the resistors in the parallel circuit. Does the same relationship exist for resistors in a parallel circuit that exists in a series circuit? Why or why not?
4. As resistors are added in parallel, what happens to the total resistance?
5. Some holiday lights are wired in parallel and others are in series. Explain how someone would be able to distinguish one from another.
PRE-LAB DISCUSSION
Elevation lines on topographic maps indicate the height a particular point on the map is above sea level. Therefore, every point on an elevation line has the same potential energy with respect to sea level. The lines may be considered to be "equipotential" lines. If a ball were placed on a hill, gravity would cause it to roll down the hill in such a way that it's direction would be perpendicular to the equipotential lines. Field lines then, are perpendicular to equipotential lines.
Whenever to charged objects are near each other, an electric field exists between them. A voltmeter may be used to determine where the equipotential lines exist between two charged objects. Once they are found the field may be drawn in perpendicular to them starting from the point of highest potential to the point of lowest potential.
PURPOSE
Show the relationship between equipotential lines and electric field lines in an electric field.
Describe various characteristics of the field between two point charges and two parallel plates.
MATERIALS
conductive paper (with objects drawn in with conductive ink) insulating pad
metal tacks connecting wires power supply
digital voltmeter
PROCEDURES
The apparatus has been previously set up by your instructor at your lab table. Do not disturb the wires where they are held in by the metal tack, this may result in a loose connection
Part A: Field Between Two Spheres
1. Plug in your power supply. Check to see that it is set at the correct voltage by touching the red probe from the voltmeter on each metal circle. One should read 14 volt, the other should read 0 volt.
2. Starting in the black area near the high potential circle (14volt) move the probe around until you find a point that reads 12 volt. Have your lab partner mark that point on his/her grid. Move the probe around until you find another 12 volt point and have your lab partner mark it. Continue this procedure until you have enough points to draw in the 12 volt equipotential line on your grid.
3. In the same manner find the 10 volt equipotential line, and continue in 2 volt increments until you reach 2 volts.
4. Now that you have all the necessary equipotential lines, draw in the field lines in colored pencil , perpendicular to the equipotential lines, starting from the point of highest potential to the point of lowest potential.
Part B: Field Between Two Plates
5. Disconnect the power supply. Pull the metal tacks and remove the conductive paper with the circles and replace it with the conductive paper with the lines.
6. Replace the tacks and wires, be sure that the tacks make a good connection with the lines.
7. Repeat procedures 1-4 with the new sheet.
ANALYSIS
1. Draw the shape of the equipotential lines in each setup.
2. Label the potential of each line.
3. Since field lines are perpendicular to equipotential lines, sketch in the field lines.
CONCLUSIONS AND QUESTIONS:
1. Are there any instances in which the equipotential lines overlap? What about the electric field lines?
2. What generalization can you make about the density of the equipotential lines in areas where you expect the field strength to be large? What happens to the field lines in areas where field strength is great?
3. What did you find about the spacing and orientation of the equipotential lines between the parallel plates? What does that indicate about the magnitude of the field between two plates?
PRE-LAB DISCUSSION
As you found in the last investigation, the shape of an electric field is determined by the shape of the conducting surfaces. In this investigation you will try to determine the shape of the conducting surface based on the orientation of field lines.
PURPOSE
To use the electric field to determine the shape of unknown charged objects.
MATERIALS
-conductive paper with conductors drawn with conductive ink on the reverse side
-digital multimeter
-DC power supply
-colored pencil
-metal push pins
-insulating board
-test leads
-grid sheets
PROCEDURES
1. Find equipotential lines in the same manner you found the lines in the last investigation.
ANALYSIS
1. Draw the shape of the equipotential lines in each setup.
2. Label the potential of each line.
CONCLUSIONS AND QUESTIONS:
1. On the grid sheet sketch the shape of the field lines that you obtained.
2. Sketch in the shape of the conducting surfaces that would produce such a field.
PRE-LAB DISCUSSION
Although many materials exhibit magnetic properties, the best permanent magnets are the metals iron, cobalt and nickel and their alloys. When two magnets are near each other they each exert a force on each other. The field concept is used to describe this interaction, in this case the magnetic field. Like unlike gravitational or electric fields, the effects of magnetic fields are easy to observe.
Since the Earth's core contains much iron, it has a magnetic field and will therefore exert a force on a permanent magnet. If a permanent magnet is allowed to rotate freely in the Earth's magnetic field it will come to rest in roughly a north-south position. The end that points north is called the magnet's north-seeking or north (N) pole, the end that points south is the south-seeking or south (S) pole.
PURPOSE
To observe the characteristics of isolated magnetic fields and the interaction of two or more magnetic fields.
MATERIALS
bar magnets (2) piece of soft iron iron nail small magnetic compass
string iron filings sheet of paper small iron washer
paper clips (steel)
PROCEDURE A: Polarity Check
Prepare an Observations Page on which to record observations and make drawings of your observations.
1. Suspend one of the bar magnets from a string. The pole marked (N) should point north when the magnet comes to rest.
PROCEDURE B: The Magnetic Field
2. Place the bar magnet on the table and cover it with a piece of white paper. Gently and evenly, sift iron filings on top of the paper. Tap the paper lightly with your finger until the filings form a definite pattern.
3. Draw the pattern observed in your Observations.
4. Notice that the filings seem to follow definite lines from one end of the magnet to the other. These lines are called field lines. Notice also that the field lines never overlap. Return the iron filings to the container.
PROCEDURE C: The Magnetic Field Between Like Poles
5. Place both magnets on the table with the N pole of one magnet about 4 cm from the N pole of the other.
6. Cover the two bar magnets with the paper and sprinkle filings onto the paper. Tap the paper lightly.
7. Draw the pattern observed in your Observations, return the iron filings to the container.
PROCEDURE D: The Magnetic Field Between Unlike Poles
8. Place unlike poles facing one another in the same way you did with like poles in Procedure C. Repeat steps 6. and 7.
PROCEDURE E: Induced Magnetism I
9. Arrange the piece of soft iron between unlike poles of the par magnets. Leave about 1.5 cm between each magnet and the piece of iron. Repeat steps 6. and 7.
10. Try the same procedure using two washers stacked on top of each other in place of the piece of soft iron.
PROCEDURE F: Induced Magnetism II
In part E, magnetism was induced in a piece of soft iron and two washers without bringing the iron or washers in contact with the magnet. A second way to induce magnetism in iron is to place it directly on the magnet.
11. Test an iron nail for magnetism by touching it to some paper clips. Touch the nail with one end of the magnet. Test the nail again while it is attached to the magnet. Record your observations.
12. With the iron nail still at one end of the first magnet, test the free end of the nail for polarity using a magnetic compass. Compare the polarity of the free end of the nail with the polarity of the end of the magnet to which it is attached. Are they the same or opposite?
PROCEDURE G: The Direction of a Magnetic Field
The direction of a magnetic field is the direction taken by the north pole of a magnet placed in the field. In general, we say that the magnetic field lines run out of the north pole and into the south pole of the magnet. To test this for yourself, test the field of one of the magnets by using a small magnetic compass.
In your Observations, draw a magnet , label the N and S poles on it, and draw in the direction in which the north seeking pole of the compass points in each step below.
13. Place the compass at one corner of the N pole and note the direction in which the north seeking pole of the compass points. Record your observations.
14. Slowly move the compass in a flattened arc from the N pole to the S pole of the magnet. Record your observations, indicating the direction of the north seeking pole of the compass for several points between the N and S pole of the magnet.
15. Place the commas between the N pole of one bar magnet and the S pole of the other. Record your observations.
CONCLUSIONS AND QUESTIONS:
1. Near what points is the magnetic field about a magnet most concentrated?
2. Describe the magnetic field between two like poles.
3. Describe the magnetic field between two unlike poles.
4. When a nail is attached to a magnet, how does the polarity of the free end of the nail compare with the polarity of the free end of the magnet?
