Here is the problem and my solution, Two spaceships each measuring 100m in its own rest frame, pass by each other travelling in opposite directions. Instruments on board spaceship A determine that the front of spaceship B takes 5x10^-6 s to traverse the full length of A. a) what is the relative velocity of the two spaceships b) how much time elapses on a clock on spaceship B as it traverses the full length of A? So for this i thought that since A is doing the measurement, it takes 5 x 10^-6 s for B to pass 100 m. Since according to A, it is still 100m. then the velocity is just 100/5 x 10^-6. is this correct? then i took this speed and put it into the time dilation equation with the 5x10^-6s to get the answer for part b. is this correct and if not how should i go about this problem, thanks.