Answer to Question #144228 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

a)

b) Reference system connected to the earth

The reference system associated with the train

If we take the reference system associated with the earth, the net force will not be zero, according to the formula shown in the figure.