Answer to Question #144695 in Mechanics | Relativity for Mikkos Joshua Garcia

Question

1. A ball is hanging from a long string that is tied to the ceiling of a train car travelling castward on horizontal tracks. An observer inside the train car sees the ball hang motionless. Draw a clearly labelled free-body diagram for the ball if (a) the train has a uniform velocity, and (b) the train is speed up uniformly. Is the net force on the ball zero in either case? Explain.

Answer 1

See Figure for Free body diagram.

Case(a) When train is moving uniformly then there is no horizontal acceleration, Hence there is no force acting in the ball.

Case(b) When train speed up then there is some net force that act on the ball, hence it will experience force.