Length of Elon’s spaceship

The proper length of Elon’s spaceship is half the proper length of Diego’s spaceship. The two spaceships are traveling in the same direction and, while both are passing overhead, Frida, an Earth observer, measures the 2 spaceships to have the same length. If the slower ship has a speed of 0.70c with respect to Frida, determine the speed of the faster spaceship, as measured by Frida.

Sample Solution