You are standing on the ground beside a railroad track. Two posts separated from each other by a distance of 125 m are fastened to the ground. As a fast train traveling at 0.6c passes by, you notice that at one instant the two ends of the train coincide simultaneously with the two posts.
a) What is the length of the train according to an observer traveling in the train?
b) According to you, how long does it take the train to pass one post?
c) What is the distance between the posts according to an observer on the train?
d) According to an observer standing at one point in the train, what is the time interval between the passing of the first and second posts?