Calculating Magnetic Field Needed for Proton Beam

[kristibella]

Homework Statement

A beam of protons is accelerated to a speed of 5.0x10^6 m/s in a particle accelerator into a uniform magnetic field. What B field perpendicular to the velocity of the proton would cancel the force of gravity and keep the beam moving exactly horizontally?

Homework Equations

B = qv/F

The Attempt at a Solution

I haven't made any attempts because I don't think that I was given enough information...

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[Delphi51]

Begin with Fg = Fb (force of gravity equals magnetic force).
Fill in the detailed formulas, then solve for what you are looking for.