- #1

- 464

- 0

## Homework Statement

What is the speed of an electron (m

_{e}=0.511 MeV/c

^{2}) with a momentum p=5 MeV/c.

## Homework Equations

Starting with momentum:

[tex]p=\gamma mu[/tex]

Then solving for u:

[tex]u=\pm\frac{cp}{\sqrt{c^2m^2+p^2}}[/tex]

## The Attempt at a Solution

I've never dealt with these units before (MeV/c

^{2}and MeV/c) so I am not sure what to do with them. Can one use those values to solve for speed? I solved it (getting 0.993c) but I converted everything to kg and kg*m/s and the solved from there.

Is there an easy way to convert (if I have to)? I ended up using a calculator online to find values. But I'd rather understand them better.

Last edited: