A metal ball with diameter of a half a centimeter and hanging from an insulating thread is charged up with 1010 excess electrons. An initially uncharged identical metal ball hanging from an insulating thread is brought in contact with the first ball, then moved away, and they hang so that the distance between their centers is 20 cm. (a) Calculate the electric force one ball exerts on the other, and state whether it is attractive or repulsive. (Enter the magnitude of the force.)N
(b) Is this force repulsive or attractive?
(c) Now the balls are moved so that as they hang, the distance between their centers is only 5 cm. Naively one would expect the force that one ball exerts on the other to increase by a factor of 42 = 16, but in real life the increase is a bit less than a factor of 16. Explain why, including a diagram. (Nothing but the distance between centers is changed -- the charge on each ball is unchanged, and no other objects are around. Do this on paper. Your instructor may ask you to turn in this work.)