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hotram

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## Homework Statement

A piece of tape is pulled from a spool and lowered toward a 170-mg scrap of paper. Only when the tape comes within 8.0 mm is the electric force magnitude great enough to overcome the gravitational force exerted by Earth on the scrap and lift it.

Determine the magnitude and direction of the electric force exerted by the tape on the paper at this distance

## Homework Equations

Coulomb's Law:

Force (electric)= k(Q1*Q2)/(r^2)

## The Attempt at a Solution

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I was not sure how to approach this problem.

But I converted 170mg=.17g and 8mm=.008m

The force is attractive, directed upward

Since k is 9*10^(9) N*(m^2)/(C^2)

and we know that the distance between the tape and the paper is .008m

I assume that we need to find the charges of the tape and the paper.

I know an electron charge is -1.602*10^(19) C

I thought that needed to see how many electrons there are in the .17g of tape. But I do not know the chemical makeup of the tape or the paper. So I don't know how many electrons there are. In other words, I am not sure how to find the charges Q1 and Q2