You are given two carts, A and B. They look identical, and you are told that they are made of the same?

Question

You are given two carts, A and B. They look identical, and you are told that they are made of the same material. You place A at rest on an air track and give B a constant velocity directed to the right so that it collides elastically with A. After the collision, both cars move to the right, the velocity of B being smaller than what it was before the collision. Is either of the carts hollow? If so, which cart?

Answer 1

Cart B has more mass. Cart A has less mass so it must be hollow.
In an elastic collision, both kinetic energy and momentum must be conserved. If the carts has the same mass, B would stop and A would move with the velocity that B had at first. If B keeps moving after the collision, it must have more mass. (Think of a train hitting a cow. The train doesn't come to a stop. Since it has much more mass than the cow, it keeps moving but slows down just a little bit.)

Answer 2

i believe A is hollow because if its an equal mass all momentum should go to cart A and therefore B shoudl stop
because it is not stopped the mass of B is greater then A which is why not all of its momentum is transfered which means that A is hollow