A ball, which we can treat as a point charge, has a charge of +Q. This ball is 50 cm away from a ball of charge-100, which is fixed in position. The +Q ball is 30 cm vertically below, and 40 cm horizontally, from the other ball, and the +Q ball is held in equilibrium at that position by a string which happens to be perfectly horizontal. Note that you should be able to do parts (a) and (b), at least, without a calculator. HINT: draw a free-body diagram. -100 30 cm 50 cm 40 cm +Q string