Question

S1. For each of the following collisions indicate whether you think momentum will be conserved. Give some justification for each.
a) A cart with a spring on it collides with a brick. The spring compresses during the collision then “springs back”. The cart is going the same speed after the collision as it was before the collision, but in the opposite direction. The brick does not move during the collision.
b) A train car is rolling slowly along the tracks. It collides with another train and they couple together so that after the collision they are moving together.

Answer 1

Hi there!

Let me help you answer this question!

Firstly, the law of conservation of momentum states that when a collision occurs between two objects 1 and 2,

the total momentum before collision must be the same as the total momentum after collision. With that said, the

momentum lost by one object is the same as the momentum ' gained' by the other object.

Here in the first case,

Since the brick was stationary through out, and the cart went back at same speed after collision, it is safe to say that momentum was conserved!

In the second case, the train car is of lower mass compared to the train itself. So when the car moves along the tracks and meets with the train, the momentum lost by the car would be seen as a slow but minute movement of the entire train, including the coupled car. Thus conservation of momentum takes place in both these cases!

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