Name _____________________
Conservation of Momentum Simulation
1. Use your web browser to:
A. Open the website http://phet.colorado.edu/sims/collision-lab/collision-lab_en.html
Choose the ADVANCED tab
OR
B. Search on “PhET”. When the PhET website is open, search on “momentum”. Select
“Collision Lab” and Choose Advanced then click on “Run Now!”
This is what
you should see.
2. Make the following changes to the simulation:
A. Click on “1-Dimension”.
B. Click on “More Data”.
C. Uncheck “Velocity Vectors”.
D. Uncheck “Center of Mass”.
This is what you
should see now.
Use the simulation to practice calculating momentum and to verifying its conservation. Enter
the Starting Conditions shown below. Be careful to ignore y, vy and py, since this is a collision in
just the x dimension. Record the momentum before (pxi) and after (pxf) the collision. You can
use the pause button to stop the action. The rewind button takes you back to the beginning.
(Note: Do not use the “Reset All” button. This will undo all of your initial set up.)
3. Same Mass, One Ball Stationary
Ball
Starting Conditions
Mass
x
vx
1
2.0
1.0
1.5
2
2.0
2.0
0
pxi
pxf
Total Momentum
A. What is the equation for momentum?
B. Show how pxi is calculated for Ball 1 (i.e. write out the equation with the numerical
values).
C. Is momentum conserved (i.e. Is the momentum the same after the collision as before
the collision? Does pxi = pxf?)?
D. What is the speed of Ball 1 after the collision?
E. What is the speed of Ball 2 after the collision? How does it compare to the speed of
Ball 1 before the collision?
4. Different Masses, One Ball Stationary
Starting Conditions
Ball
Mass
x
vx
1
4.0
1.0
1.5
2
1.0
2.0
0
Total Momentum
A. Show how pxf is calculated for Ball 2.
B. Is momentum conserved?
C. What is the change of momentum, p, for Ball 2?
pxi
pxf
5. Same Mass, Balls Traveling in Opposite Directions
Ball
Starting Conditions
Mass
x
vx
1
2.0
1.0
1.0
2
2.0
2.0
-1.0
pxi
pxf
Total Momentum
A. Describe what happens to Ball 1’s direction, velocity and momentum after the collision.
B. Is momentum conserved?
6. Different Masses, Balls Traveling in Opposite Directions
Ball
Starting Conditions
Mass
x
vx
1
6.0
1.0
1.0
2
1.0
2.0
-1.0
pxi
Total Momentum
A. Does Ball 1’s direction reverse after the collision as it did in #5?
B. Is momentum conserved?
C. What is p for Ball 2?
D. What is the impulse received by Ball 2?
E. What is the value of Ft (the force times time) for Ball 2?
pxf
7. Completely Inelastic (Sticky) Collision with Same Masses
Now adjust the elasticity from 100% to 0%. This is a completely inelastic collision, such as
when two pieces of clay collide and stick together.
Ball
Starting Conditions
Mass
x
vx
1
2.0
1.0
1.0
2
2.0
2.0
-1.0
pxi
pxf
Total Momentum
A. Describe what happens to the balls after the collision?
B. Is momentum conserved?
8. Completely Inelastic (Sticky) Collision with Different Masses
Keep the elasticity at 0%.
Ball
Starting Conditions
Mass
x
vx
1
6.0
1.0
1.0
2
1.0
2.0
-1.0
Total Momentum
A. Is momentum conserved?
pxi
pxf