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## Homework Statement

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 I am trying to solve, and this leads to 2 unknowns in 1 equation. If anyone can give me a hint I would appreciate it.