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## Homework Statement

*A train passes a platform with velocity v. Two clocks are placed on the edge of the platform separated by a distance L and synchronized relative to the platform inertial system.*[Emphasis mine]

**Clock 1 reads 4:00 when it coincides with the front of the train, and clock 2 reads 4:00 when it coincides with the rear of the train.**Answer questions relative to an observer on the train.(a) What is the length of the train?

(b) What is the reading of the clock 2 when clock 1 coincides with the front of the train?

(c) What is the time interval between the two end events?

## Homework Equations

Lorentz Transformations

## The Attempt at a Solution

Before answering a, b and c, I actually need to understand this question. Here are my qualms:

1. If the part of the question in bold refers to observations from the platform frame, then I don't understand how the clocks can be synchronised. The clocks read 4:00 at different times(events).

2. If it refers to observations from the train, then it seems to me to be in contradiction with what the author says a few pages earlier. It is proved that given a pair of clocks, which are synchronised in a frame in which they are at rest, moving in the the same direction and separated in space, the leading clock lags behind the trailing one(the exact amound being Lv/c

^{2}, L- measured distance between clocks). If that is true, then howcome clock 1(leading clock) reads 4:00 before clock 2(trailing).

What am I missing?

For those interested, this is problem 2.4 from Richard Mould's

*Basic Relativity*(Springer).