1. Calculate the net charge on an arbitrary substance consisting of

a. 5 x 10^4 electrons

b. a combination of 7 x 10 ^13 protons and 4 x 10^13 electrons

2. Each of two spheres 6.0 x 10^-2 m apart carries a charge of +2.0 x 10^-6 C.

a. Calculate the force between them.

b. Is the force attractive or repulsive?

3. A 2.2 uC charge is located on the x-axis at x=-1.5 m. A 5.4 uC charge is located on the x-axis at x=2.0 m. A 3.5 uC charge is at the origin. Find the net force acting on the 3.5 uC charge.

4. Two electric charges originally 8cm apart are brought closer together until the force between them is greater by a factor of 16. How far are they apart now?