Question

A balloon rubbed against denim gains a charge of -8.0C. What is the electric force between the balloon and the denim when the two are separated by a distance of 5.0 cm? (Assume that the charges are located at a point.)

Answer 1

The quantity of electrostatic force between point charges is described by Coulomb's law.

$F=k\frac{q_1\cdot q_2}{r^2}$ where $k=9×10^9 N⋅m^2⋅C^{−2}$ , $r=5.0cm=0.05m$

When electrified by friction, two bodies exchange charges. So there was a charge left on the denim +8.0C.

$F=9\cdot 10^9Nm^2C^{-2} \frac{-8.0C \cdot 8.0C}{(0.05)^2 m^2}=-2.3\cdot 10^{14}N$

Answer: The electric attractive force between the balloon and the denim is $2.3\cdot 10^{14}N$  

_{PS: It is possible that the value of the charge is incorrectly specified in the problem condition, which is why such a large force is obtained.}