# Answer to Question #11980 in Mechanics | Relativity for Nur hasyimah

Question #11980

Dear respectable experts, please help me solve this question..im dying.. Thank you
The distance between the two trolleys and that between the 1-unit mass trolley and the wall at t = 0s are both d.
The two trolleys are both moving at the same speed V towards each other initially and they collide head on with each other at t = 5s.
Immediately after the collision, both trolleys bounce off in opposite direction and the 1-unit mass trolley reaches its original position at t = 9s.
Both trolleys continue their motion and the 1-unit mass trolley eventually hits the wall and bounces back at the same speed at which it hits the wall.
At what time will the 1-unit mass trolley hit the 2-unit mass trolley again? (You may assume that friction force is negligible throughout the motion of the two trolleys)

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