What is solution of following problem:
Problem: A small sphere with mass 9.00 ?g and charge ?4.30?C is moving in a circular orbit around a stationary sphere that has charge +7.50?C.
A- If the speed of the small sphere is v = 6100m/s , what is the radius of its orbit? Treat the spheres as point charges and ignore gravity.
I don't just need an answer, work and explanations/walkthrough would be much appreciated! Thanks.