# A Relativity Problem

1. Sep 29, 2006

### actionintegral

A line of people are moving at the same speed, clocks all sync'd. They agree that at a certain time they will stop! Let's pretend they can stop
instantaneously.

Relativistically speaking, what will we who are at rest see?

2. Sep 29, 2006

### lightarrow

Their clocks are syncronized in their ref. frame but not in our. So, we will see they don't all stop at the same time: we will see the one at the end of the line (relative to the direction of motion) stopping first, the one at the head of the line stopping last. So, the total lenght of the line, after they have stopped, is the same as the lenght in their ref. frame when they're moving.

3. Sep 29, 2006

### actionintegral

4. Sep 29, 2006

### Staff: Mentor

What madness? That's exactly what JesseM has been saying throughout that thread.

5. Sep 29, 2006

### actionintegral

You are right. And you have too, I see. I was referring to the fact that
the thread is into three pages and growing! It seems to me that the question as posed was too complex and led to the self-perpetuating confusion of the original poster.

6. Oct 3, 2006

### bernhard.rothenstein

acceleration

have please a critical look at

Radar echo, Doppler Effect and Radar detection in the uniformly accelerated reference frame
Authors: Rothenstein, Bernhard; Popescu, Stefan
The uniformly accelerated reference frame described by Hamilton, Desloge and Philpott involves the observers who perform the hyperbolic motion with constant proper acceleration gi. They start to move from different distances measured from the origin O of the inertial reference frame K(XOY), along its OX axis with zero initial velocity. Equipped with clocks and light sources they are engaged with each other in Radar echo, Doppler Effect and Radar detection experiments. They are also engaged in the same experiments with an inertial observer at rest in K(XOY) and located at its origin O. We derive formulas that account for the experiments mentioned above. We study also the landing conditions of the accelerating observers on a uniformly moving platform.
Comment: 15 pages, 8 figures, includes new results on radar detected times and distances
Full-text available from: http://arxiv.org/abs/physics/0609118