basically i have a small charged sphere on the left, and at a certain horizontal distance away from it theres a bigger sphere that is made of a thin shell of nonconducting material. the bigger sphere (B) is hanging from a non conducting, uncharged thread, and that thread makes an angle of 20 degrees with the vertical when sphere B is in equilibrium. centers of the sphere are at the same vertical height and are 1.5m away from each other. the small sphere(A) has a charge of 120microCoulumns, and the larger sphere has radius of .05m and mass of .025kg what is the charge on sphere B? now i think if i set up an equation where the potential energy of sphere B ( since the thread hanging it is not vertical, B has a vertical displacement caused by the electric field b/t the two spheres) is equal to the electric field generated by the two spheres, i can figure out the charge on B. but i wasnt given the length of the thread, so that prevent me from getting the vertical displacement of sphere B. but i wonder why the mass and radius of the sphere B was given tho.. any clue on where to tackle this problem?