So how would I implement this as equations? Something like the ball travels from ##(L,L/u)## in Alice's coordinates to ##(0,2L/u)## and then transform these points to Bob's reference frame and use the velocity of the ball as seen by Bob? Or is there something else I'm missing?
a) Alice is observing a small ball of mass m in relativistic motion
bouncing elastically back and forth between two parallel walls separated by a distance L
with speed u. After each collision it reverses
direction, thereby creating a clock. What does Alice observe as the...