# Homework Help: Radii for a circular path of a proton.

1. Sep 24, 2008

### Lance WIlliam

1. The problem statement, all variables and given/known data

Find the radius of the circular path described by a proton moving at 15 in a plane perpendicular to a 400- magnetic field.

2. Relevant equations

I used the Eqn: r=mv/qB
So (1.67e-27)(15ooom/s)/(1.60e-19)(400) and I go 6.265e-2 m

but the answer is in mm so im i correct to just say 6.265e-5
since mm is e-3 and its alrdy e-2m
is my answer even right though?

2. Sep 24, 2008

### buffordboy23

I don't know the magnitude of the quantities for your problem, so I can't say if your answer is right. You didn't specify them; 400 T, 400 mT, etc.?

Anyways, your equation is correct; shift your decimal point one position to the right and you will get 62.65e-3 m, which is equivalent to 62.65 mm.

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