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## Homework Statement

Suppose that resting on your non-conducting desktop is a tiny piece of paper(m=0.08g) that carries a charge of +4 x 10

^{-10}C. You comb your hair and then slowly lower your comb until when it is 3 cm away from the paper, the paper jumps up to the comb.

a) Give an approximate value for the charge on the comb.

b) Does the comb carry an excess of electrons or protons? How many?

## Homework Equations

Coulomb's Law:

F=(1/4*pi*E

_{0})*(|Q

_{1}Q

_{2}|/r

^{2})

Magnitude of charge of electron and proton: e=1.60217 x 10

^{-19}

Q=ne

## The Attempt at a Solution

I know that we have to consider w=mg since there is mass involved for the paper. I tried to use Coulomb's Law to find the charge, but I don't know what the Force is between the two, so how can I find charge for the comb? I've converted the given numbers to the right units which are 0.08g = 0.8 x 10

^{-4}and 3cm = 0.03m.

Now, my question is, can anyone give me a hint on how to start this question?