>
> Right... So if I let q and Q be the charge of my ball and magnet (what's
the
> correct unit for charge?),

Coulombs (C)

> and I measure r in meters, then F will come out
> in Netwons?

Newtons. Yup.

>While we're on the subject, what would be a suitable range of
> magnitude for q and Q? (The ball is 80g in mass.)

Quite small. The electrostatic forces are very strong

eg. If you give one ball a charge of 5*10^-5 C and the other a charge
or -5*10^-5C and put them a metre apart the force between them is 22.5 N
That's equivalent to the gravitational force exerted by the earth on an
object of
mass 2.2kg.

If you charge a plastic rod by rubbing it with fur you can typically get a
charge
of 10^-9 C

Gail
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