An electron has a kinetic energy of 7.00 10-17 J. It moves on a circular path that is perpendicular to a uniform magnetic field of magnitude 4.40 10-5 T. Determine the radius of the path?

Answer 1

you know the equation for force in a magnetic field for a moving particle. Find force.

then set that force equal to centripetal force, mv^2/r, and solve for r.