physics
posted by Anonymous .
At a certain location on the Earth,
the horizontal component of the Earth’s magnetic field is 2.5 ·10−5 T due North. A proton moves
eastward with just the right speed for the magnetic force on it to balance its weight so the net
force on the proton will be zero. Find the speed of the proton for this to occur.

e V B = m g
since the directions of V and B are perpendicular
m is the proton mass and e is its charge. g is the acceleration of gravity
Solve for V