Question

A bead with a mass of 0.085 g and a charge of 20 nC is free to slide on a vertical rod. At the base of the rod is a fixed 20 nC charge.
In equilibrium, at what height above the fixed charge does the bead rest?

Answer 1

Let the charge separation be x. The elecrostatic repulsion force must equal the weight.

k*(20*10^-9)^2/x^2 = M g

M = 85*10^-6 kg
g = 9.8 m/s^2
k is the Coulomb constant. (You may need to look it up. If you are studying elctricity, your text will say what the value is.)

Solve for x

Answer 2

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