Marcus tries to move a refrigerator but can't. Has he done work?
Yes, because he used energy.
No, because he did not move the object.
Yes, because he exerted a force.
No, because he did not use energy.

Two carts, one of mass 2m and one of mass m, approach each other with the same speed, v. when the carts collide, they hook together. assume that positive momentum is to the right. which graph best represents the momentum of both carts over time, before and after the collision?