- #1

- 784

- 11

## Homework Statement

If the kinetic energy of a particle is equal to twice its rest energy, what percentage error is made by using p = mu for the magnitude of its momentum?

## Homework Equations

[tex]\[E_i=mc^2\][/tex]

[tex]\[p = \frac{mu}{(1-\frac{u^2}{c^2})^\frac{1}{2}}\][/tex]

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

[tex]\[K=\frac{p^2}{2m}\][/tex]

## The Attempt at a Solution

I set K = 2mc^2 and then solved for the relative velocity u and ended up with u=(2/sqrt(5))*c

I then set K = 2mc^2 again but this time the momentum term was non relativistic, and solving for u I got u = 2c

now i'm lost