Conservation of Momentum
Explosion Lab
Name:___________________________________
Mod:____________
Date:____________
Pre-Lab Questions:
1. State the conservation of momentum.
2. What factors influence the momentum of an object?
3. Is it possible for tractor trailer and a matchbox car to have the same momentum? Explain
why or why not.
4. In the lab, how many trials are completed for each scenario?
5. In the lab, what is the band width of the picket fence?
Purpose:
- To demonstrate that momentum is conserved with two carts pushing away from one
another.
Materials:
-
PAScar Carts (2)
Dynamic Metal Track
Adjustable End Stops (2)
Adjustable Track Feet (2)
Triple-Beam Balance
-
250g Car Mass (2)
Photo Gate (2)
Picket Fence (2)
Data Studio w/ Interface Box
Theory:
When two carts push away from one another (and there is no net force on the system), the
total momentum is conserved. If the system is initially at rest, the final momentum of the
two carts must be equal in magnitude and opposite in direction to each other so the
resulting total momentum of the system is zero. Refer to the equation below:
𝑝 = 𝑚1 𝑣1 − 𝑚2 𝑣2 = 0
Procedure:
1. Insert the Photo gate bracket on both ends of the dynamic track at the 90cm and 30cm
mark. Attach the photo gate head to the bracket. Adjust the height of the photo gate so
that the sensor passes through the smallest part of the picket. This can be done by
inserting the picket fence on top of the cart (make sure the small picket is facing upward)
and placing it under the photo gate as a reference.
2. Insert the adjustable track feet on both ends of the dynamic track at the 10cm mark and
110cm mark. Level the track by adjusting the feet if needed.
3. Insert the adjustable end stops at both ends of the dynamic track at the 5cm and 115cm
mark. Face the end stops so that the magnetic side faces away from the center of the
track.
4. Plug the photo gate sensors into Port 1 and Port 2 of the interface box. Make sure the
interface box is turned to the on position.
5. Record the mass of the cart with the picket fence attached to the top using the balance.
Record the data in Table A.
Conservation of Momentum Explosion Lab
Methacton High School Physics Department
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6. Place the carts on the track with one of the carts front bumpers facing towards the other
cart. The other cart should have the bumper facing away for the car. This will keep the
Velcro from sticking together and causing errors in the data. Reference Figure 1.1
7. Push the bumper in on both of the carts and lock it. Using the measurements found on
the track, place the two carts in the middle of the track at the 60cm mark. Reference
Figure 1.1
8. Open up Data Studio on the computer and click, “Create Experiment.” Follow this by
dragging the mouse over to “Experiment” found in the upper left hand corner and
choosing, “Change Interface.”
9. Choose Science Workshop 500 and click “Ok.”
10. The computer screen should now show the interface box. Click the yellow circle on Port
1 and choose “Photo Gate and Picket Fence.” Un-check position and acceleration on the
table under measurements and adjust the band spacing to 0.005m under constants.
Complete the same thing for Port 2.
11. Double click “Graph” located on the left side of the screen and a box will appear. Click
“Velocity Ch 1” in the box and press okay. A graph should appear. Double click
“Graph” again and complete the same thing for Channel 2.
12. Press the start button located in the top left hand corner to start collecting data.
13. Release the bumper to create the explosion to cause the carts to separate. A finger can be
used to push the button, but be cautious since the finger could cause the cart to slow a
little.
14. Once each cart passes underneath the photo gate, press the stop button at the top. Record
the velocity of each cart in Table A. Remember velocity is a vector quantity which
requires direction. Right is positive and left is negative.
15. Complete two more trials for a total of three for the two cart explosions and record the
velocities in Table A.
16. Next, add the masses to each of the carts on the track and find their mass using the
balance. Record the mass in Table B. Complete the same steps as above for a total of
three trials and record the velocities of the carts in Table B.
17. Now take the mass off one of the carts and leave the other on. Complete the same steps
as above for a total of three trials and record the velocities and mass of the carts in
Table C.
18. Find the average of the total momentum and record it in each of the tables.
Conservation of Momentum Explosion Lab
Methacton High School Physics Department
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Data Tables:
Trial
Cart 1
Mass (kg)
Cart 2
Mass (kg)
No Mass Added to Carts
Table A
Cart 1
Cart 2
Cart 1
Cart 2
velocity
velocity momentum momentum
(m/s)
(m/s)
(kgm/s)
(kgm/s)
Total
momentum
1
2
3
Avg.
Momentum
Trial
Cart 1
Mass (kg)
Cart 2
Mass (kg)
Mass Added to Carts
Table B
Cart 1
Cart 2
Cart 1
Cart 2
velocity
velocity momentum momentum
(m/s)
(m/s)
(kgm/s)
(kgm/s)
Total
momentum
1
2
3
Avg.
Momentum
Trial
Cart 1
Mass (kg)
Cart 2
Mass (kg)
Mass Added to One Cart
Table C
Cart 1
Cart 2
Cart 1
Cart 2
velocity
velocity momentum momentum
(m/s)
(m/s)
(kgm/s)
(kgm/s)
Total
momentum
1
2
3
Avg.
Momentum
Conservation of Momentum Explosion Lab
Methacton High School Physics Department
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Post-Lab Questions: Answer the following questions by writing in complete sentences. If the
question asks you calculate or solve, show your work and circle the final answer with the correct
units.
1. What is the total momentum before the collision? How does the total momentum before
the collision compare to the total momentum after the collision? Explain.
2. Calculate the percent error for the total momentum for each of the scenarios. The actual
total momentum is zero and the calculated total momentum is the average found in each
of the scenarios.
𝐴𝑐𝑡𝑢𝑎𝑙 − 𝐶𝑎𝑙𝑐𝑢𝑙𝑎𝑡𝑒𝑑
|
| 𝑥100 = _______%
𝐴𝑐𝑡𝑢𝑎𝑙
3. Did adding the extra mass to one of the carts affect the total momentum after the
collision?
4. When the carts of unequal masses push away from each other, which cart has more
kinetic energy?
5. What factors do you think may have led to errors between the momentum before the
explosion and the momentum after the explosion? Give at least three errors and explain
how they can be corrected if the experiment were to be completed again.
Conservation of Momentum Explosion Lab
Methacton High School Physics Department
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