E.29.03. Relativity Practice Problems Two spaceships pass each other in opposite directions. the speed of spaceship B as measured by a passenger in spaceship A is 0.6c. The passenger in B measures spaceship B to be 30 m long while measuring spaceship A to be 20 m long. What are the lengths of the two spacecraft as measured by a passenger in spaceship A? The two spacecraft cease their relative motion and passengers A and B meet for lunch. Whose spacecraft takes up more space in the parking lot? How long would observer A say that it takes B's spaceship to pass her? How long would observer B say that it takes A's spaceship to pass him? A 100-m train travels at a speed of 60 mi/hr. By what factor will a car stopped at the railroad crossing measure the train length to be longer or shorter? At Fermilab in Illinois, protons are accelerated to such speeds that gamma is approximately 200. The particles move in a circular path (due to magnetic fields) of radius 1 km. Find v/c for the protons. How much time will a round trip take for a lab scientist? How much time will round trip take for a proton?