A simplified account of special relativity and the twins paradox.
Have you got the Mach knack? Discover the mathematics behind exceeding the sound barrier.
A messenger runs from the rear to the head of a marching column and back. When he gets back, the rear is where the head was when he set off. What is the ratio of his speed to that of the column?
Calculate the paths of raindrops flying up from the back tyre of a bicycle