Question

Which of the following are true about energy or momentum conservation?
(A) When two marbles collide on a frictionless surface, their total momentum is conserved
(B) When two marbles collide on a frictionless surface, their total mechanical energy is conserved
(C) When a perfectly elastic ball is dropped on a surface its total mechanical energy remains constant
(D) When two cars collide, their total momentum just before and after is same.

Answer 1

Answer:

D is the correct option

Answer 2

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(D) When two cars collide, their total momentum just before and after is same.