Name:
Laboratory investigation
Conservation of momentum and kinetic energy during elastic and inelastic collisions. Please stay on
task:
Part 1
1. Open the Phet Collision simulation: http://phet.colorado.edu/sims/collision-lab/collisionlab_en.html
2. Click on “1 Dimension”, “more data”, and “momenta diagram”. Make sure the elasticity is at
100%.
3. Choose three random situations for velocities and masses for your two objects, run the
simulation each time and record the resulting velocities (do not forget the signs). Choose your
values at manageable levels so you can follow the objects easily
4. Record each trial neatly below. For each trial draw a labeled sketch (before and after masses
and velocities) and calculate the total momentum before and after the collision. The before and
after states should be one after another, without any of the objects touching the walls! Does the
total momentum conserve? Are they equal? Each time? If yes, circle the answer.
a. Trial 1:
b. Trial 2:
c. Trial 3:
5. Choose a few more situations that are special:
a. Make one object have a large mass and be at rest. Do not exaggerate the mass value,
the object should fit in the area designed for it. The other should be tiny, moving
towards the larger object. Predict what will happen if the objects collide. Is the
momentum still conserved? Show your calculations below:
b. Set the objects equal in mass to each other. One also at rest. Try to predict what will
happen and then verify your prediction by running your experiment. Is the momentum
conserved? Show your calculation and sketch below:
Part 2
6. Run two more experiments as you did above (random) or use the numbers you obtained already
and check to see if the total kinetic energy before and after is also conserved. Show your work
below:
7. Change the elasticity to 50% (or any other number more than 0 and less than 100%). Run a
random case. Check for the conservation of momentum for the situation. Draw the sketch and
label physical quantities like above.
8. Verify (for part 7) if the total kinetic energy is conserved:
9. Change the elasticity to 0%. Run again a random case and draw the sketch. Check for the
conservation of momentum and kinetic energy in this case:
Part 3 (done as bonus)
10. Click on 2 Dimensions. Change the elasticity to 100%.
11. Play with the simulation a little bit to get the feel for it. As you can see, we have a 2 dimensional
case (the objects do not necessarily remain along a single line before and/or after they collide).
You are to design a procedure to find out if the conservation of momentum and kinetic energy
hold in this case. Please show your explanations and calculations below (hint – you need to
decompose each momentum vector along a set of axes conveniently chosen)
12. Repeat for elasticity equal to 0%.