# Magnetism Physics Question

Hey yall:

So I ran across this confusing question and was wondering if you guys could help me out.

Consider the fact that you have a positive particle (which would be q=1.6E-19) that is traveling at 1.9E4 m/s perpendicular to a 1.0 x 10-3 T magnetic field. If the radius is .40m what is the particles mass?

I don't understand how the 1.0 x 10-3 T can be used in any calculation! Is that just 1.0E8 T, or am I really missing something? Any formulas would be appreciated.

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## Answers and Replies

Doc Al
Mentor
I don't understand how the 1.0 x 10-3 T can be used in any calculation! Is that just 1.0E8 T, or am I really missing something?
Unless it's a misprint, they meant 1.0 x 10-3 T, which is the same as 1.0E-3 T.

Any formulas would be appreciated.
How do you find the magnetic force on a moving charge? Look up the Lorentz force.

Think about how the magnetic force interacts with a moving charge. It moves along in a circle, so we can say that the magnetic force is the centripetal force on the particle. Using the two equations, one can find an equation that solves for the mass of the particle in terms of the velocity, magnetic field, and radius.

EDIT: oh, and the charge :p