Question

Hiro rubs an inflated balloon on his hair, and his hair sticks to the balloon. As he moves the balloon away from his head, how does the electric force change?

The electric force increases because the balloon loses its charge.
The electric force increases because the distance increases.
The electric force decreases because the distance increases.
The electric force decreases because his hair loses its charge.

Answer 1

The electric force decreases because the distance increases.

By Coulomb’s law F = k q1 q2 / r^2: with the charges essentially fixed, increasing the separation r reduces the force (it falls off roughly as 1/r^2).