Question

please anyone solve this for me

Answer 1

Let the initial charges be q and q' respectively. Now, after the contact is made the charges are rearranged (as spheres are of unequal and opposite charges) such that they acquire same charge, let us say Q. Now, it is such that Q = (q - q')/2

so, after they are again brought apart at a distance of 0.9 m, the force between them will be given as

F = kQ2 / r2

or

0.025 = (9x109 x Q2) / 0.92

or

Q2 = 0.025 x 0.92 / 9x109

thus,

Q = (2.25 x 10-12)1/2

so, final charge on each of the spheres will be

Q = 1.5 x 10-6 C


hope this helps u....