> Coulombs (C)

OK, so tell me people - *is* there a "u" in that or not? ;-) Some seem to
think there is, others not...

> >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

So I recall... "A person jumps off the top of a building. It takes him 30
seconds to accelerate down to the bottom under gravity, but only a fraction
of a second for electrostatic forces to bring his bode to a half again.
[Presumably rearranging it beyond recognition in the process!]"

> 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.

Ah... yes, *charge balls*... I had _better_ remember to give them OPPOSITE
charges... presumably they'll repell instead of attract otherwise? (Hmm...
that might actually be useful later on...)

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

So I take it a 1C is a fairly large charge then? (I remember hearing that 1
Farrid is larger than any capacitor ever built - "built" being the word!)

> Gail

Thankyou very much!

So, in summary, I have three "magnets" (at least, fixed points which I want
to "attract" a moving particle). Right... so I need r in meters, q and Q
with opposite sign and at around about 10^-7 C or so, and the formula will
give me an answer in Newtons which should be halfway sane (assuming I make
sure that r stays away from zero!) Right, will try...

Thanks again for all the people who bothered to help a hapless half-brain!
Andrew.

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