Momentum and Collisions Phet Simulation
http://phet.colorado.edu/sims/collision-lab/collision-lab_en.html
The menu in the upper right corner will allow you to toggle quite a few displays. You may find putting check
marks in velocity vectors and momentum vectors helpful. Choosing show values will also provide you with the
“real time” values for velocity and momentum during the simulation. This also where we will control how
elastic the collisions are.
Clicking on the “more data” button will bring up the following display
This will allow you more control over the initial conditions for the objects.
Elastic Collision Investigation:
1) What do we need to see mathematically to prove/justify a collision is elastic?
Simulate the four elastic collision below (be sure elasticity is set to 100%). Complete the table using math and
the simulation. The “before collisions” items must be determined before you can run the simulation. Feel free
to use the simulation to get your values for “after collision” from the simulation. Show any needed work in the
space below the data table.
#
1
m1
2.0 kg
m2
2.0 kg
2
2.5 kg
5.0 kg
3
3.0 kg
6.0 kg
4
6.0 kg
BEFORE COLLISION
v1
v2
1.5 m/s
-1.0 m/s
2.0 m/s
0.0 m/s
2.0 m/s
-1.0 m/s
ptotal
0 kg·m/s
AFTER COLLISION
v1
v2
0 kg·m/s
8.0 kg·m/s
2) Two objects with the same mass move towards each other with the same magnitude of their velocities
and experience an elastic collision. Qualitatively compare the final velocities of each object to their
initial velocities (be sure to comment on both magnitude and direction)
3) A less-massive moving object has an elastic collision with a more-massive object that is not moving.
Qualitatively compare the initial velocity (speed and direction) of the less-massive object to its final
velocity.
Partially Inelastic Collision investigation:
For this simulation please set the Elasticity to 40%
You are going to redo the same four scenarios as before, so your “before collision” values will just transfer
down. You will need to run your simulation to get the “after collision values”
#
1
m1
2.0 kg
m2
2.0 kg
2
2.5 kg
5.0 kg
3
3.0 kg
6.0 kg
4
6.0 kg
BEFORE COLLISION
v1
v2
1.5 m/s
-1.0 m/s
2.0 m/s
0.0 m/s
2.0 m/s
-1.0 m/s
ptotal
0 kg·m/s
AFTER COLLISION
v1
v2
0 kg·m/s
8.0 kg·m/s
For scenario 4 in both the elastic and partially inelastic collisions calculate and compare the total initial kinetic
energy of the system to the final kinetic energy of the system. What did you find was true for elastic that was
not true for the partially inelastic?
One more on the next page
Totally Inelastic Collisions
Simulate the four elastic collision below (be sure elasticity is set to 0%). Complete the table using math and
the simulation. The “before collisions” items must be determined before you can run the simulation. Feel free
to use the simulation to get your values for “after collision” from the simulation. Show any needed work in the
space below the data table.
BEFORE COLLISION
#
1
m1
2.0 kg
m2
2.0 kg
v1
1.5 m/s
v2
0
2
3.0 kg
6.0 kg
1.5 m/s
-0.75 m/s
3
1.5 kg
5.0 kg
2.0 m/s
0.2 m/s
4
10.0 kg
2.0 m/s
-1.0 m/s
AFTER COLLISION
ptotal
v1 and v2
10.0 kg·m/s
Two objects moving toward each other with different momentums experience an inelastic collision. In which
direction will both objects travel after the collision? (Provide a qualitative response).
If two object are traveling towards each other and stop as a result of their totally inelastic collision, what must
be true?