Question

How to express the mass of a proton and an elektron in MeV/c²? Thank you!

I know how to express something in MeV/u and I know how much c² is... But i can't make up my mind how to do this?

Answer 1

This is a bit sneaky - it’s physics shorthand, that’s all.

Explanation:

As you know mass and energy are inter-convertible (`E=mc^2`) and an energy can also be expressed as a charge multiplied by a p.d. (voltage) as `E = Q.V`

This means that physicists often express the masses or energies of subatomic particles in eV, but of course if we rearrange the first equation for mass we get `m = E/c^2` so formally all energies quoted in eV (or MeV, GeV etc.) should actually be quoted as `(eV)/c^2` but laziness prevents it and it is just quoted as eV.

Sorry.