E field 3

Would it be possible to make one charged ball orbit another in a space station?

For an entry to a competition to make an experiment to run in the international space station, a student suggests putting a small charged body in orbit around a big one (like a simple atomic model). He has two metal spheres, one with radius 5 cm and mass 1 kg and the other with radius 0.5 cm and mass 10g. He decides to charge the sphere with a static electricity generator which his teacher (me) has said creates a potential of 100 kV.  The experiment must fit into the space station so an orbital radius of 15 cm is chosen.

Calculate the orbital speed of the small ball.

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