(a) Two insulated charged copper spheres A and B have their centresseparated by a distance of 50 cm.

(a) Two insulated charged copper spheres A and B have their centres
separated by a distance of 50 cm. What is the mutual force of
electrostatic repulsion if the charge on each is 6.5 × 10–7 C? The
radii of A and B are negligible compared to the distance of
separation.
(b) What is the force of repulsion if each sphere is charged double
the above amount, and the distance between them is halved?