When would I use the equation ##E = \gamma mc^2## and when would I use ##E^2 = (mc^2)^2 + (pc)^2##? I'm a little confused because my textbook calls them both total energy equations. I know that for a particle at rest it has energy ##E=mc^2##. It can't be at rest for the equation ##E = \gamma mc^2## because ##\gamma## involves velocity, so I assume the object has to be moving. So when do I use that equation? And when do I use the ##E^2## one?(adsbygoogle = window.adsbygoogle || []).push({});

Thanks for any help! :)

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# I When to use each of these relativistic energy equations

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