A spacecraft with a proper length of 300m takes 0.75E-6s to pass an earth observer. Calculate the speed of the spacecraft as measured by the earth observer.
The Attempt at a Solution
I'm not sure how to get this, when you plug in those numbers you get 4E8m/s, which is faster than the speed of light. This makes me think that one of the given data needs to be adjusted, but length/time changes all include u, which is what im trying to solve, and this leads to 2 unknowns in 1 equation. If anyone can give me a hint I would appreciate it.