Three railway cars of equal mass are on the same (frictionless) track. The one on the left is moving with velocity V toward the other two which are stationary. As the cars undergo successive collisions, they couple and move together. What is the velocity of the final configuration of the three coupled cars?
A)V
B)V/2
C)V/3
D)V/4

Question

Quizplus · Accepted Answer

The velocity of the final configuration of the three coupled cars is V/3 due to the conservation of momentum. Since all cars have equal mass and the system is closed (no external forces), the total momentum before and after the collisions must be the same. Initially, only one car has momentum (mass * velocity), and after all collisions, the total mass is three times larger while the momentum remains constant, leading to a final velocity of V/3.

Three Railway Cars of Equal Mass Are on the Same