Objective:
Part A – To investigate the relationship between impulse and the change in momentum and to prove that they are equal to each other.
Part B – To prove the law of conservation of momentum for different collisions and situations.
Apparatus: 2 Pasco cars with track, force sensor, 2 motion sensors, computer
Procedure:
1.
Acquire 1 track and 2 Pasco cars
2.
If your group is modifying the mass of the cars (see Mr. Pagett), acquire the additional mass to put on the cars.
3.
Get 2 USB links, 2 motion sensors and 1 force probe out of the bins.
4.
Attach both USB links to your computer
Part A –
1.
Attach 1 motion sensor (make sure the motion sensor is on the cart setting) and the force probe to the USB links.
2.
Open the 11 Impulse CF.ds file.
3.
Set up your track on a slight incline (put one end of the track on top of 1 or 2 books)
4.
Put the motion sensor on the raised end to measure the velocity of the cart.
5.
Put the force sensor on the other end so that the cart will collide with the bumper a.
NOTE: you must secure the force sensor (prop it against the wall) so that it will not move during the collision.
6.
Make sure the force probe is zeroed before each trial
7.
Click the start button and allow the cart to accelerate down the incline and impact the force probe.
8.
Two graphs will be illustrated – a velocity vs. time graph and a Force vs. time graph.
9.
Record the change in velocity from the graph and record the area under the
Force vs. time graph.
10.
Calculate the change in momentum of the cart and compare it to the impulse.
11.
Repeat trial as necessary to get good data.
Part B – 1) Totally Inelastic Collision
1.
Replace the force sensor with the other motion sensor and level the track.
2.
Open the 09 Conserve Momentum CF.ds file
3.
Put one cart in the middle of the track (v i
= 0 m/s)

4.
Start recording data and give the other cart a push so that it has a velocity.
5.
The carts should hit and stick together
6.
Stop recording data after the collision
7.
Look at the graphs and record the velocity of the pushed cart right before the collision and the velocity of the other cart right after the collision.
8.
Calculate the momentum of the 1 st cart before the collision and the momentum of the two carts after the collision and compare.
9.
Repeat trial as necessary to get good data.
Part B – 1(a) “Elastic” Collision
1.
Turn the carts around so that the plungers will collide and allow the carts to
“bounce off” of each other.
2.
Start recording data and give both carts a push.
3.
The carts should hit and bounce off.
4.
Stop recording data after the collision
5.
Look at the graphs and record the velocity of the pushed carts right before the collision and after the collision.
6.
Calculate the momentum of the carts before and after the collision and compare.
7.
Repeat trial as necessary to get good data.
Part B – 1(b) “Elastic” Collision
8.
In this part of the lab you will add one bar mass to one of the carts.
9.
Start recording data and give both carts a push.
10.
The carts should hit and bounce off.
11.
Stop recording data after the collision
12.
Look at the graphs and record the velocity of the pushed carts right before the collision and after the collision.
13.
Calculate the momentum of the carts before and after the collision and compare.
14.
Repeat trial as necessary to get good data.

Data:
Part A –
Item
Mass of PAScar, m:
Impulse (Area under force-time curve):
Change in velocity, Δ v:
Calculated change in momentum, m Δ v:
% difference
Part B1 –
Item
Mass, Cart 1 (m
1
):
Value
Value
Mass, Cart 2 (m
2
):
Initial Velocity, Cart 1 (v
1
):
Initial Velocity, Cart 2 (v
2
):
Combined Velocity (v’):
Calculations: Calculate the momentum before and after the collision
Before Collision
After Collision
Total Momentum
% difference

Part B2 (a) –
Item
Mass, Cart 1 (m
1
):
Mass, Cart 2 (m
2
):
Initial Velocity, Cart 1 (v
Final Velocity, Cart 1 (v
1
1
):
’):
Value
Initial Velocity, Cart 2 (v
2
):
Final Velocity, Cart 2 (v
2
’):
Calculations: Calculate the momentum before and after the collision
Total Momentum
Before Collision
After Collision
% difference
Part B2(b) –
Item
Mass, Cart 1 (m
1
):
Mass, Cart 2 (m
2
):
Initial Velocity, Cart 1 (v
1
):
Value
Final Velocity, Cart 1 (v
1
’):
Initial Velocity, Cart 2 (v
2
):
Final Velocity, Cart 2 (v
2
’):
Calculations: Calculate the momentum before and after the collision
Total Momentum
Before Collision
After Collision
% difference

Questions:
Part A –
1) Why does the velocity of the cart change from a positive value before the collision to a negative value after the collision?
2) What is the significance of the area under the curve for the force versus time graph?
3) How does the area under the curve for the force-time graph compare to the change in momentum?
4) What are some possible reasons why the calculated change in momentum is not the same as the measured impulse?
5) Why is it important to know the value of the change in velocity?
Part B –
1) How do your values of total momentum compare before and after the collision?
2) What are some reasons why the momentum after collision may not have been the same as the momentum after the collision?
3) What can you conclude about the relationship between the momentum before and after an inelastic collision?
4) Do your results support the Law of Conservation of Momentum?
Conclusion: