You see a 2.1 kilogram car (call it #1) moving on a frictionless track. There is another car (#2) of unknown mass which is at rest. The two cars collide, lock, and move together. A friend says that that the cars have equal masses. You think that is not necessary. You make a bet.Your challenge is to calculate the mass of car #2.

STINK: (Stop and Think!) What physics principle do you think you should apply. Hint: What principle do we usually apply to collisions and explosions?

After you have a plan of attack, go to this link: (Find the mass), perform the experiment, and write up the lab including a proper diagram, a procedure, the measurements, and your conclusion about the mass of car #2. Could you have answered who wins the bet even if you did not know the mass of car #1? That would be AMAZING!