Question

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 15.7 mg piece of tape held 0.72 cm above another. (The magnitude of this charge is consistent with what is typical of static electricity.)

Answer 1

Step-by-step explanation:

Let the equal charges be Q .

Force between charges = k Q² / R where R is distance between charges , k = 9 x 10⁹.

Putting the charges

Force F = 9 x 10⁹ x Q² /( .72 x 10⁻²)²

= 17.36 x 10¹³ Q² N

This force equals weight so

17.36 x 10¹³ Q² = 15.7 x 10⁻³

Q² = .90 x 10⁻¹⁶

Q = .95 x 10⁻⁸

= 9.5 x 10⁻⁹

= 9.5 nC.