Una carga de -3 µC y otra de 2 µC en el vacío están separadas 4 cm.
A. Calcula la magnitud de la fuerza electrostática que ejerce una de las cargas sobre la otra.
B. Dibuja la fuerza electrostática que actúa sobre cada carga.
C. Calcula la magnitud de la fuerza electrostática si las cargas estuvieran en vidrio.

A) 33.8 N

B) Attractive force (see graph)

C) 158.9 N

Explanation:

A)

The magnitude of the electrostatic force between two electric charges is given by

where

k is the Coulomb's constant

q1, q2 are the magnitudes of the two charges

r is the separation between the charges

Here in this problem, we have:

is the magnitude of the 1st charge

is the magnitude of the 2nd charge

r = 4 cm = 0.04 m is the separation

Substituting, we find the magnitude of the force:

B)

Find the graph showing the direction of the force in  attachment.

The direction of the electrostatic force between two charges is given as follows:

- If the two charges have same sign (++ or --), the force is repulsive

- If the two charges have opposite sign (+-), then the force is attractive

In this problem:

- Charge 1 is negative

- Charge 2 is positive

The two charges have opposite signs: therefore, according to the rules above, the electrostatic force between them is attractive.

C)

When the charges are placed in a medium, the magnitude of the electrostatic force between the two charges increases due to the polarization effect on the medium, and the new force is given by

where:

F is the original electrostatic force in a vacuum

is the relative permittivity of the medium

Here in this problem, we have:

F = 33.8 N is the original electrostatic force

is the relative permittivity of the medium (glass)

Therefore, the new electrostatic force between the charges is

F' = (33.8)(4.7) = 158.9 N