Three charged particles lie in the xy plane at an angle of θ relative to the x-axis. Charge q1 is located at the origin, q2 is a distance r from q1, and q3 is a distance 3r from q1. The charges each have magnitude of q, but q1 = q2 = +q, and q3 = -q. Charges q1 and q3 are fixed, and q2 can move. However, q1 and q2 are connected by an ideal, neutral spring of spring constant ks. The spring is initially not stretched. Let Coulomb’s constant be ke. q1 and q2 are positive and q3 is negative. (a) Choose the best expression for the net electrostatic force on q2, in terms of the given variables.
(b) Because the force on q2 is nonzero, it will begin to move from rest. In which direction will it move?
(c) When q2 begins to move, it will stretch the spring. Choose the equation for the force vector from the spring, Fs, due to stretching the spring a distance of Δr.
(d) When q2 is at its equilibrium position, the forces acting on it will be balanced. Which of the expressions below correctly shows the electrostatic force on q2 when the charge has reached its equilibrium position?