(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

Suppose one photon has an energy of 200 MeV and it is traveling along the x-axis. Suppose another has an energy of 100 MeV and is traveling along the y-axis. (A) What is the total energy of this system. (The answer is 300 MeV) (B)If a single particle has this same energy and momentum, what would be its mass?

The answer is 200 MeV, I am having trouble reaching that answer.

2. Relevant equations

[tex]p=\frac{E}{c}[/tex] for a photon

[tex]p={\gamma}mu[/tex] for a particle with mass

[tex]E=cp[/tex] for a photon

[tex]E={\gamma}mc^{2}[/tex] for a moving particle with mass.

3. The attempt at a solution

Energy of the photon = energy of the moving particle:

[tex]cp={\gamma}mc^{2}[/tex]

[tex]300 MeV={\gamma}mc^{2}[/tex]

Momentum of the photon = momentum of the moving particle:

[tex]\frac{E}{c}={\gamma}mu[/tex]

[tex]\frac{300 MeV}{c}={\gamma}mu[/tex]

This is all I can do so far, after this I get stuck. If I continue, I get the result that u=c. The correct answer is u=.74c

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# Homework Help: Photon energy, momentum, and velocity

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