1. The problem statement, all variables and given/known data A tiny sphere with a charge of q = +6.1 µC is attached to a spring. Two other tiny charged spheres, each with a charge of -4.0 µC, are placed in the positions shown in the figure, in which b = 3.6 cm. The spring stretches 5.0 cm from its previous equilibrium position toward the two spheres. Calculate the spring constant. (See attachment) 2. Relevant equations Coulomb's law: F = Kq1q2/r^2 Spring Constant: F = kx 3. The attempt at a solution I determine the net force due to to the individual force caused by F1 and F2: F1 = kq1q2/r^2 * < cos(a), -sin(a) > F2 = kq1q2/r^2 * < -cos(a), -sin(a) > Fnet = F1 + F2 Where q1 = 4E-6 C, q2 = 6.1E-6 C, r = .0412 m ( by Pythagorean theorem) , a = 61 degrees Fnet = < 0, -3.8E-1 > ||Fnet|| = 3.8E-1 N ; This is force due to the two charges pulling down on the spring. F = kx Sub in values: 3.8E-1 = k*(.036) ===> k = 11 The spring constant is 11 N/m ?