Question

A 2.0 mm diameter glass sphere has a charge of +1.0 nC. What speed does an electron need to
orbit the sphere 1.0 mm above the surface? (Ans. 2.81×107 m/s)

Answer 1

So the electron is 2mm from the center.

set coulombs force= centripetal force
kQ1*e/r^2=m v^2/r
solve for v