- #1

warfreak131

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## Homework Statement

A particle is observed in a certain reference frame (i.e. observer A) has a total energy of 5GeV and a momentum of 3GeV/c.

(a) What is the energy of the frame in which its momentum is equal to 4GeV/c.

## Homework Equations

[tex]E'={\gamma}E-{\gamma}{\beta}(cp)[/tex]

[tex]cp'=-{\beta}{\gamma}E+{\gamma}(cp)[/tex]

## The Attempt at a Solution

I plugged in cp'=4GeV, cp=3GeV, and E=5GeV, and solved the second equation for v. Then I plugged in v to the applicable variables in the first equation, and I got 4GeV, but the answer is 5.62GeV. And a different part of the question asks for the relative velocity of the two frames, and for that I get .6 c, as opposed to .19 c.