Question

Trolley B will be at rest and trolley A will be given a push such that it collides with B, and they both move as one mass after the collision. As soon as the blocker of the picket fence on trolley A passes through the eye of the first photogate, trolley A must collide with trolley B, and immediately after collision, the blocker on the picket fence of trolley B must enter the eye of the second photogate.

1)Why must the collision take place immediately after blocker A leaces the eye of the photogate?
2) Why must blocker B enter the eye of the photogate immediately after collision?

1) So that the photogate could record the velocity before the collision. Blocker A also will have time to gain momentum
2) So that we know the velcocity immediately after the collision other wise veolocity will be lost if it wasn't immediately afet the collision.

Are my answers correct. I am not sure whether 1) or 2) is correct. Thanks for helping me out. I really apprecitate it.

Both are correct answers.