(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

A train passes a platform with velocity v. Two clocks are placed on the edge of the platform seperated 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?

2. Relevant equations

Lorentz Transformations

3. 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 seperated 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'sBasic Relativity(Springer).

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# Homework Help: Help Me Understand this SR Question

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