Two charged spheres are 20 cm apart and exert an attractive force of 8 x 10-9 n on each other. what will the force of attraction be when the spheres are moved to 10 cm apart?

Explanation:

The inital electrostatic force between the two spheres is given by:

where

is the initial force

k is the Coulomb's constant

q1 and q2 are the charges on the two spheres

r is the distance between the two spheres

The problem tells us that the two spheres are moved from a distance of r=20 cm to a distance of r'=10 cm. So we have

Therefore, the new electrostatic force will be

So the force has increased by a factor 4. By using , we find

the area between the graph and the t axis