Crossfire in an accelerating railway carriage.

Discussion in 'Physics & Math' started by Confused2, Jun 19, 2016.

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  1. James R

    James R Just this guy, you know? Staff Member

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    39,426
    Spacetime curvature.

    At any given moment in time there is no difference between the velocity of the two sides. However, if the bullet starts on the right and ends on the left, obvious the left-hand side will be going faster than the right-hand side by the time the bullet hits it. But then you're dealing with two different times, not one.

    Time dilation is an effect of changing your frame of reference. It's something you see from one reference frame when you look at measurements of time being made in some other reference frame.
     
    James R, Jun 21, 2016
    #21

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  3. Confused2

    Confused2 Registered Senior Member

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    So, if the sides of the carriage are joined by the structure of the carriage then each point on one side remains in the same frame as the equivalent point on the other side? By 'same frame' we mean 'Same Inertial frame' as in the SR definition of 'same frame'?

    So, can we consider the joining both sides by an iron bar across the carriage ? - that is at right angles to the track and at right angles to the direction the locomotive applies a force to accelerate the carriage.

    With the carriage stationary we synchronise a large number of little clocks and spread them over the iron bar and on the other side of the carriage. All sychronised. The carriage is then accelerated at a m/s/s for the duration of the next observations. The claim both sides of the carriage are going at the same speed suggests there will be no change - the clocks will remain precisely sychronised. Of course they will be synchronised again if we stop the train or simply stop accelerating but what happens while the carriage is accelerating is rather crucial to observing 'an effect' or 'no effect'. So any effect or no effect on the clocks?

    Stop the train. Now place the same bar is placed parrallel to the tracks bar A end at the front (pointing towards the locomotive) and B towards the back. Sync all the clocks again and spread them out over the bar. Now apply acceleration a in the direction BA. Again, what do the clocks show - any effect or no effect?
     
    Confused2, Jun 21, 2016
    #22

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  5. Janus58

    Janus58 Valued Senior Member

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    Clocks on the bar at a right angle to the acceleration remain in sync whether under acceleration or not.
    Clocks on the bar parallel to the acceleration run at different rates, with clocks in the direction of the acceleration running faster than those in the other direction. The further apart two clocks are from each other, the greater the difference in their tick rate.
     
    Janus58, Jun 21, 2016
    #23
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