Coulomb’s Law Practice problems – Group Work (scribe and solvers)
Solve problems on large paper. Work in groups of three. The scribe (person that is doing the writing)
follows the instructions of the other group members. Take turns acting as scribe.
1. (Show your work clearly) Given two charged particles (q1= -0.42 C, q2= -0.15C), separated by a
distance of 0.22m, what is the force that exists between them? Is it attractive or repulsive?
2. (Show your work clearly) An electron and a proton are positioned such that there is a force of 1N of
attraction between them. How far apart are they?
3. Suppose that two equally charged spheres attract each other with a force of 0.492 N when placed a
distance of 29.1 cm from each other. Determine the charge of the spheres.
4. A balloon has been rubbed with wool to give it a charge of -1.0 x 10-6 C.
A plastic tube with a charge of +4.0 x 10-6 C is held a distance of 0.50 m
above the balloon. Determine the electrical force of attraction between
the tube and the balloon.
a. Construct a free-body diagram showing the direction and the type of all
forces acting upon the 30.0-gram balloon.
b. Will the balloon accelerate up, down, or not at all? _____________
c. If there is an acceleration, then calculate its value. (Assume that the plastic
tube is held a constant distance of 0.5 m from the balloon.)
5. Determine what size charge is needed (q1) for the 2.2 μC (mass 1.3 g) charge to remain suspended
0.5 cm above the ground. (see picture).
2.2 C
q1
1) 1.17x1010 N
4a) FE up and mg down
2) 1.52x10-14 m
4b) downward
3) 2.2 μC (2.2x10-6 C)
4c) 5 m/s2
4) 0.144 N
5) 1.6x10-11 C