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Electricity and Magnetism

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Moderate

Repulsion Between Charged Objects

EANDM-KO3NUU

Two equally charged foam balls each of mass $ m = 2.5\:\rm g$ hang in equilibrium from a thread of length $ L=15 \: \rm{cm}$ as shown in the figure below. Assume the radius of each foam ball is much less than $L$ (the figure is NOT to scale).

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Determine the charge, $Q$, on each ball.

A

$7.8 \:\text {nC}$

B

$6.12 \times 10^{-15} \:\text C$

C

$210 \:\text {nC}$

D

$4.4 \times 10^{-15} \:\text C$

E

$66 \:\text {nC}$