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Simultaneity question: light in a moving spaceship

  • Thread starter senorhosh
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  • #1
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Homework Statement


Spaceship with proper length 100m is moving at 0.2c in +x direction. In the back and front of the spaceship is a light source.
a. When the light in the back is turned on, how long will it take for the light to reach the front of the spaceship?
b. How about the light in the front? (to reach the back)

Homework Equations





The Attempt at a Solution


a. I'm guessing because light always moves at c in all reference frames, t = d/c or 100/c? There would be no time dilation or length dilation because light is moving the same frame as the space ship
b. Same answer as a. for the same reasons.

For some reason, I don't think this is correct. I'm not sure why... it just seems off..
Any help? thanks.
 

Answers and Replies

  • #2
Doc Al
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I suspect they want the time it takes for the light to travel according to the frame that views the rocket as moving at 0.2c.
 
  • #3
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I suspect they want the time it takes for the light to travel according to the frame that views the rocket as moving at 0.2c.
Whoops I forgot to add this in.
"Measured by the frame of the spaceship". So no..
sorry about that. Anyway would my answer be correct then?
 
  • #4
Doc Al
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44,882
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Whoops I forgot to add this in.
"Measured by the frame of the spaceship". So no..
sorry about that. Anyway would my answer be correct then?
Yes, in that case your answers are correct: the time of travel is simply 100m/c in each direction. (From the frame of the rocket, the rocket is at rest.)
 

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