SP212
Worksheet 1
Ch 21.(1-3) Coulomb’s Law
Problem 1
Three particles are placed on the x-axis. Particle 1 has charge q1 = +4Q and is placed at the origin.
Particle 2 has charge q2 = −2Q and is placed a distance L to the right of particle 1. Particle 3 has
charge q3 = q and is placed a distance L to the right of particle 2. In terms of k, Q, q, and L what is
the magnitude and direction of the net force acting on particle 3? (assume that Q > 0 and q > 0).
This problem is is relevant to HW L1 Problem 7.
Problem 2
A charge of size q1 = 4µC is placed at the origin in the xy plane. A second charge of size q2 = −1µC
is placed at the point ~r = 4cmî + 3cmĵ. (1µC = 10−6 C)
a) In component vector form, what is the force acting on charge 2 due to charge 1?
b) If a third charge of size q were added to this system, where would you have to place it so that the
net force acting on it was zero? You may assume the third charge is positive, q > 0.
HINT: The third charge will need to be located somewhere along the line that goes through both
charge 1 and charge 2. (Think about why this would be.)
This problem relates to HW L1 Problem 15.