What is the minimum magnitude of an electric field that balances the weight of a plastic sphere of mass 14.2 g that has been charged to 7.7 nc. give your answer to the nearest 0.1 mn/c (mega newton per coulomb)

18.1 MN/C

Explanation:

The gravitational force of the plastic sphere is in equilibrium with the electric force.

Mass of the plastic sphere = m = 14.2 g = 0.0142 kg

Force of gravity = F = mg = (0.0142)(9.81) = 0.139 N

This force is balanced by the electric force due to the charge 7.7 nC

Charge = q = 7.7 x 10⁻⁹ C

Electric field = E = F / q = (0.139) /(7.7 x 10⁻⁹) = 18.1 MN/C

answer: what are you talking about?

explanation:

speed of light in vacuum is 300,000 km/s

speed of light in other mediums is given by the expression v = c/n, where c is the speed of light in vacuum and n is the refractive index of medium.

for the first medium v = 200,000 km/s

  so, refractive index of medium = 300000/200000 = 1.5

    1.5 refractive index is usually for glass. so first medium is glass.

for the second medium v = 250,00 km/s

so, refractive index of medium = 300000/250000 = 1.2

    1.2 refractive index is usually for water. so second medium is water.

for the third medium v = 0 km/s

so, refractive index of medium = 300000/0 = ∞

    ∞ refractive index is usually for opaque mediums. so third medium is opaque medium.