Two identical carts are placed on a frictionless track. Cart 1 is initially at rest while Cart 2 is moving to the right towards Cart 1. The two carts collide elastically. After the collision, which of the following is true?
I. Carts 1 and 2 are both at rest
II. Cart 2 stops and cart 1 moves to the right with speed equal to the original speed of cart 2
III. Cart 1 remains at rest and cart 2 bounces back with speed equal to its original speed
IV. Cart 1 moves to the right with a speed slightly less than the original speed of cart 2 and cart 2 moves to the right with a very small speed