Physics: 5 problems, Electric Forces and Electric Fields

See attached file.

1. An electron is released a short distance above Earth's surface. A second electron directly below it exerts an electrostatic force on the first electron just great enough to cancel the gravitational force on it. How far below the first electron is the second?

2. Three charges are arranged as shown in the Figure Find the magnitude and direction of the electrostatic force on the 6.00nC charge. See the attachment.

3. The electric field everywhere on the surface of a thin spherical shell of radius 0.750m is measured to be equal to 890N/C and points radially toward the center of the sphere.
a) What is the net charge within the sphere's surface?
b) What can you conclude about the nature and distribution of the charge inside the spherical shell?

4. A small 2.00g plastic ball is suspended by a 20.0cm long string in a uniform electric field, as shown in the figure #2. If the ball is in equilibrium when the string makes a 15.0 degree angle with the vertical as indicated, what is the net charge on the ball? See attachment.

5. Two small silver spheres, each with a mass of 100g, are separated by 1.00m. Calculate the fraction of the electrons in one sphere that must be transferred to the other in order to produce an attractive force of 1.00*10^4N (about a ton) between the spheres. (the number of electrons per atom of silver is 47, and the number of atoms per gram is Avogadro's number divided by the molar mass of silver, 107.87)