This PSSC film made in 1960 is one of the finest physics films ever made. All students should see it at some point in their studies. See the article '"Frames of Reference" revisited' by Alistair Steyn ...
Shown below is an animation of the motion of A and B as seen by a stationary observer. The paths of A and B are straight, as expected, with the speed of B increasing in time. View of B as seen by an ...