What is the electric force between a glass
ball that has +1.2 × 10^−6 C of charge and a
rubber ball that has −3 × 10^−6 C of charge
when they are separated by a distance of
4.7 cm? The value of the Coulomb constant
is 8.98755 × 10^9 N · m^2
/C^2
.
Answer in units of N.
F = k Q1 Q2 / d^2
= 9*10^9 * 1.2*10^-6 * -3*10^-6 / [ 4.7^2 * 10^-4 ]
the - sign means they pull toward each other. (like charges repel)