1. The problem statement, all variables and given/known data In a certain inertial frame two light pulses are emitted a distance 5 km apart and separated by 5 µs. As observed from another frame, which is travelling parallel to the line joining the points where the pulses are emitted at a velocity v with respect to this frame, the pulses are simultaneous. Find v. 2. Relevant equations 3. The attempt at a solution i know this should be very simple, but i am so stuck!