An alpha particle (m = 6.68×10-27 kg, q = 3.20×10-19 C) circularly orbits a charged sphere at a radius of 5.00 cm from the sphere's center. The electric attraction between the two objects provides the centripetal force to keep the particle in orbit. The orbital speed of the particle is 6.480e+4 m/s. What is the charge on the sphere?