Check here to show the center of mass

INSTRUCTIONS - For a particular collision between two carts on a straight track, there are nine bars representing what happens with the momentum during the collision. Three are shown (always two for cart 1 and then one of the others). For the other six (identified with circular handles), your job is to drag them left or right to show their values correctly. Note that one or more of these may actually be zero. When you think all six are correct, check your answer to see if you are correct. Once you have correctly solved the puzzle, try another set. See if you can get 10 sets correct before your "Incorrect" score reaches 4.

HINTS - You may find it helpful to hit Play to see the collision take place - that might help you to set the bars correctly. After you get good at it, set the bars without viewing the collision, and then try to predict what the outcome of the collision will be.
You only get credit for a Correct answer when all six bars are correct. Note that the ends of the bars should always line up with the grid lines.
Are any of the bars always zero no matter what?

BACKGROUND - Three of the momentum bars are for cart 1 - the momentum before the collision, the momentum transferred to cart 1 during the collision, and the momentum after the collision. There are a similar three for cart 2, and another three for the two-cart system. Note that there is no net external force acting on the two-cart system. This means that the momentum of the system should be conserved in the collision. What else does this imply about how different bars are related to one another?

Simulation first posted on 6-07-2018. Written by Andrew Duffy