Question

A piece of tape is pulled from a spool and lowered toward a 100-mg scrap of paper. Only when the tape comes within 8.0 mm is the electric force magnitude great enough to overcome the gravitational force exerted by Earth on the scrap and lift it.

Requried:
Determine the magnitude and direction of the electric force exerted by the tape on the paper at this distance.

Answer 1

The magnitude of the electric force is
`F_e = 0.00098 \ N`

Step-by-step explanation:

From the question we are told that

The mass of the paper is
`m= 100 mg = 100 *10^(-6) \ kg`

The position is
`d = 8.0\ mm = 0.008 \ m`

Generally the magnitude of the electric force at the point of equilibrium between the electric force and the gravitational force is mathematically represented as

`F_e = F_g = mg`

Where
`F_g` is gravitational force

substituting values

`F_e = 100 *10^(-6) * 9.8`

`F_e = 0.00098 \ N`

Now generally the gravitational force acts downward (negative y axis ) hence the reason the electric force is same magnitude but opposite in direction (upward + y - axis )