Common transparent tape becomes charged when pulled from a d

Common transparent tape becomes charged when pulled from a dispenser. If one piece is placed above another, the repulsive force can be great enough to support the top piece\\\'s weight. Assuming equal point charges (only an approximation), calculate the magnitude of the charge if electrostatic force is great enough to support the weight of a 14.0 mg piece of tape held 1.00 cm above another.

Solution

magnitude of electric force = weight

kq²/r² = mg

q² = mgr²/k = 1.524 x 10^-18

q = 1.235 x 10^-9C