Introduction to Classical Mechanics · Problem 11.32
Relativity (Kinematics) — Morin
Physics — Mechanics · walking-on-a-train
Problem
A train of proper length L and speed 3c/5 approaches a tunnel of length L. At the moment the front of the train enters the tunnel, a person leaves the front of the train and walks (briskly) toward the back. She arrives at the back of the train right when it (the back) leaves the tunnel.
(a) How much time does this take in the ground frame?
(b) What is the person's speed with respect to the ground?
(c) How much time elapses on the person's watch?