Special Relativity - relative motion of two bars

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Homework Help Overview

The discussion revolves around a problem in special relativity involving two bars of the same proper length moving along the x-axis. The original poster is tasked with finding the relative velocity of the two bars based on a given time interval between events observed in the reference frame of one of the bars.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants question how two bars can have a nonzero relative velocity if they are moving in the same manner. There is a suggestion to find the length of the second bar in the frame of the first bar as a function of their velocity, and to explore the relationship between this length, the velocity, and the time interval Δt.

Discussion Status

The discussion is ongoing, with participants exploring different interpretations of the problem and questioning the assumptions made about the motion of the bars. Some guidance has been offered regarding the relationships between the variables involved, but no consensus has been reached.

Contextual Notes

There is a mention of a requirement for participants to show their work, indicating a potential constraint on how solutions can be approached. Additionally, a reference to a similar question on another platform suggests that this problem may not be unique, but it does not provide further resolution.

John Sellars
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Misplaced Homework Thread: post moved from technical forums, so no template
Hi, I'm stucked in this exercise. I don't know how to proceed. Any hints I appreciate it.Two bars of the same proper length L, moves in the same way on the x axis. In the referential of one of the bars the time interval between the events, when the extremity right of one bar and the extremity left of other bar is equal to to Δt. Find the relative velocity of the the two.
 
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How can they have a nonzero relative velocity if they move in the same way?
John Sellars said:
In the referential of one of the bars the time interval between the events, when the extremity right of one bar and the extremity left of other bar is equal to to Δt.
The grammar in that sentence looks broken.

Find how long the second bar is in the frame of the first bar (as function of the velocity v). Then determine how that length, the velocity and Δt are related. That should lead to some equation for the velocity that you can solve.
 
Someone else is asking this question:
https://physics.stackexchange.com/questions/590423/special-relativity-relative-motion-of-two-objects
 

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