Relativistic Velocity Transformations

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Homework Help Overview

The discussion revolves around a problem in relativistic physics, specifically concerning the velocity of a proton emitted from a quasar moving away from Earth at a significant fraction of the speed of light. Participants are exploring how to correctly apply relativistic velocity transformations to find the proton's speed relative to the quasar.

Discussion Character

  • Conceptual clarification, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants are questioning the validity of simply adding velocities in a relativistic context, with one participant expressing confusion about whether the Lorentz transformation would yield a speed relative to the Earth or the quasar. Others are discussing the need to consider the signs of the velocities when applying the transformation.

Discussion Status

There is an active exploration of the problem, with participants providing guidance on the use of Lorentz's equations and emphasizing the importance of understanding the reference frames involved. No consensus has been reached yet, but the discussion is progressing with clarifying questions and suggestions.

Contextual Notes

Participants are operating under the constraints of relativistic physics, specifically the limitation that no object can exceed the speed of light. The problem setup includes known velocities relative to Earth, which adds complexity to the transformation process.

jayjay713
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A quasar is moving away from the Earth with a speed of 0.850C. It emits a proton that eventually reaches earth, and is traveling at a speed of 0.519C relative to the earth. How fast is the proton moving relative to the quasar?

Is this answer as simple as it seems?

is the answer simply 0.850 + 0.519 = 1.369C?
i am confused
thanks for any help
 
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No, you can't have a speed greater than c.
In relativity, you must use Lorentz's velocity transformation equations.
 
but if I used that formula, wouldn't it give me a speed relative to the earth? Or would it be relative to the quasar? :O
 
jayjay713 said:
but if I used that formula, wouldn't it give me a speed relative to the earth? Or would it be relative to the quasar? :O

Well you know the quasars velocity relative to the Earth and you know the protons velocity relative to the earth. So you know the protons velocity in the Earths rest frame, and you can lorentz transform it into the quasar rest frame using the quasar velocity. Don't forget the signs of the velocities! Post your answer when you have worked it out :)
 

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