Coulomb's law problems?

Question

1. How many electrons should be removed from a neutral object to give it a charge of = 1 uC?

2. How far apart should two electrons be placed so that the force of repulsion between them is
(a) 1N
(b) same as the weight of an electron on the surface of the earth

3. Two small metal spheres initially neutral are placed 3.0m apart. Now one billion electrons are transferred from one sphere to the other. Determine the charge on each sphere and the force between them.

4. The force of repulsion between two point charges placed 6.0m apart is 5.0 * 10^9 N. If one charge has twice the magnitude of the other, determine those magnitudes.

5. Two point charges of +6 uC and - 4 uC are placed in a plane at the points (6m,-2m) and (0m,4m). Determine the magnitude and the direction of force on each.

Answer 1

1) 6.25 x 10^12

2) You can use-:

Force = q1 x q2 / (4 x pi x Epsilion0 r x r)

q1 and q2 are the charges
Epsilon0 = 8.85 x10^-12
r is the distance of separation between the charges
4 is well 4
and Pi is (22 / 7)

Its a simple equation to use.