Irodov Problem 1.352

a) Let the proper length of the rod be lo. Since the rod is moving at a speed v with respect to frame K, the length of the rod as seen from Frame K would be lesser than its proper length and equal to . At time instant tA, the front end of the rod was at xA. This implies that the rear end must have been at . At time tB, the rear end of the rod was at xB, this implies that the rear end of the rod moved a distance of in a time interval of tB - tA. Since the rod was moving at a speed v, we have,








b) In order to determine the time interval required to measure the proper length of the rod in equation (1) we can set xB - xA = lo, and we have,