Name _________________________________ Period _____
Coulomb's Law Practice Problems
1. Suppose that two point charges, each with a charge of +1 Coulomb are separated by a distance of
1 meter. (a) Will they attract or repel? _______________(b) Determine the magnitude of the electrical
force between them.
9 x 109 N
2. Two balloons are charged with an identical quantity and type of charge: -0.0025 C. They are held
apart at a separation distance of 8 m. Determine the magnitude of the electrical force of repulsion
between them.
878.9 N
3. Two charged boxes are 4 meters apart from each other. The blue box has a charge of +0.000337 C
and is attracting the red box with a force of 626 Newtons. Determine charge of the red box. Remember
to indicate if it is positive or negative.
0.0033 C
4. A piece of Styrofoam has a charge of -0.004 C and is placed 3.0 m from a piece of salt with a charge
of -0.003 C. How much electrostatic force is produced?
12,000 N
5. Two coins lie 1.5 meters apart on a table. They carry identical electric charges. Approximately how
large is the charge on each coin if each coin experiences a force of 2.0 N?
2.24 x 10-5
Name _________________________________ Period _____
6. The electron and proton of a hydrogen atom are separated, on average, by a distance of about
5.3 x 10-11 meters. Find the magnitudes of the electric force and the gravitational force that each particle
exerts on the other.
Fg = 3.6 x 10-47 N
Fe = 8.2 x 10-8 N
Mass of electron = 9.109 x 10-31
Mass of proton = 1.673 x 10 -27
Charge of electron = -1.60 x 10-19 C
Charge of proton = +1.60 x 10-19 C
Which force is stronger, the gravitational force or the electric force? ____________________________
For the following question: Use 1.60 x 10-19 C for the charge of an electron.
7. Determine the quantity of charge on …
a. … a plastic tube which has been rubbed with animal fur and gained 3.8x109 electrons.
b. … a vinyl balloon which has been rubbed with animal fur and gained 1.7x1012 electrons.
c. … an acetate strip which has been rubbed with wool and lost 7.3x108 electrons.