Proton AND Work-Energy Theorem

[SsUeSbIaEs]

Can some one help me out here, I have tried using several different methods but I still don't know what I am doing wrong.

The question is:

A proton in a high energy accelerator moves w/a speed of 0.5c, use the work-energy theorem to find the work required to increase its speed to 0.7c.


I have tried /\K=.5m(vf^2-vi^2), what am I doing wrong????

[cookiemonster]

You're not taking into account relativistic effects.

cookiemonster

[SsUeSbIaEs]

I don't know what your talking about,

I thought I would use:

.5m( (.7*c)^2-(.5*c)^2)

c= the speed of light

I was also told an equation like m^2c^2((1/sqrt(1-(v^2/c^2)))-1), but I kept geting zero for my answer and the actual answer is like 3.69??e-11, but I do not know how they got this answer??

[Doc Al]

Originally posted by SsUeSbIaEs
.5m( (.7*c)^2-(.5*c)^2)
This is only correct for low, non-relativistic speeds.
I was also told an equation like m^2c^2((1/sqrt(1-(v^2/c^2)))-1) ...
Use the relativistically correct expression for KE:
KE = mc^2((1/sqrt(1-(v^2/c^2)))-1)