An observer O is standing on a platform of length L = 90 m on a station. A rocket train passes at a relative (constant) speed of 0.96c moving parallel to the edge of the platform. Then, the observer O found that the front and back of the rocket train simultaneously line up with the ends of the plat form at a particular instant. A. In the rest frame of the observer O, what is the time necessary for the rocket train to pass a particular point on the platform?
B. What is the rest length lo of the rocket train?
C. According to another observer O on the rocket train, what is the length L of the platform?
D. Again, according to observer O' on the rocket train, how long does it take for observer O to pass the entire length of the rocket train?

Your starship, the aimless wanderer, lands on the mysterious planet mongo. as chief scientist-engineer, you make the following measurements: a 2.50-kg stone thrown upward from the ground at 14.0 m/s returns to the ground in 5.70 s ; the circumference of mongo at the equator is 2.20×10^5 km ; and there is no appreciable atmosphere on mongo. (a) the starship commander, captain confusion, asks for the following information: what is the mass of mongo? (b) if the aimless wanderer goes into a circular orbit 2.20×10^4 km above the surface of mongo, how many hours will it take the ship to complete one orbit? (c) an unmanned spacecraft is in a circular orbit around the moon, observing the lunar surface from an altitude of 44.0 km . to the dismay of scientists on earth, an electrical fault causes an on-board thruster to fire, decreasing the speed of the spacecraft by 23.0 m/s . if nothing is done to correct its orbit, with what speed (in km/h) will the spacecraft crash into the lunar surface?