Question

Two point charges separated by a distance d repel each other with a force of 9N. If the separation between them becomes 3d, the force of repulsion will be?

Answer 1

it is clear that,force is inversely proportional to sqaue of distance.Hence when distance becomes 3d, r² will become 9d.Our new force will be 1N

Answer 2

Explanation:

It is given that,

If two point charges separated by a distance d repel each other with a force of 9 N. There exists a electrostatic force between two charges. It can be given as :

$F=k\dfrac{q_1q_2}{d^2}$

i.e. electrostatic force is inversely proportional to the square of distance.

Initially,

$9=\dfrac{k}{d^2}$............(1)

Finally,

$F'=k\dfrac{q_1q_2}{(3d)^2}$............(2)

Dividing equation(1) and (2)

F'= 1 N

If the separation between them becomes 3d, the force of repulsion will be 1 N. Hence, this is the required solution.