Energy, momentum and CM

  • Thread starter Tonyt88
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  • #1
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So I have this problem:
A mass m travels to the right at 4c/5, and another mass m is at rest.

They ask fro the energy and momentum of each particle, so I have:

Energy of traveling: 5/3 mc^2

Energy of rest: mc^2

Momentum of traveling: 4mc/3

Momentum of rest: 0

Then they ask for the velocity of the CM of the system:

Which I have 2c/5, but then some people are telling me c/2.

But anyway, I have to solve for the velocities of the particles in the CM frame, so how I do go from there.
 

Answers and Replies

  • #2
dextercioby
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What is the definition of the center of mass for a relativistic system of point particles...?

Daniel.
 
  • #3
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1/M (x1m1 + x2m2) ?
 
  • #4
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It should be the "zero momentum" frame.
 
  • #5
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Then I really don't know what to say, but I would like to know, if you have the value for the velocity at the CM (which I think is either 2c/5 or c/2), how do I go from there to solve for the resultant velocities?
 
  • #6
dextercioby
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You just need the CM's velocity. You've been hinted that in the CM frame the total momentum of the particles is zero.

Daniel.
 

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