It takes 10 s and 15 s, respectively, for two trains travelling at different constant speeds to completely pass a telegr...

Question

It takes 10 s and 15 s, respectively, for two trains travelling at different constant speeds to completely pass a telegraph post. The length of the first train is 120 m and that of the second train is 150 m. The magnitude of the difference in the speeds of the two trains (in m/s) is:

A. 2.0
B. 10.0
C. 12.0
D. 22.0

Accepted Answer

The magnitude of the difference in speeds is 2.0 m/s (Answer A). When a train passes a point (like a telegraph post), it travels a distance equal to its own length. Speed equals that length divided by the time taken. Once we have both speeds, we subtract to find the difference. This is a straightforward application of speed = distance / time.