1. The force of attraction that a -40.0 ?C point charge exerts on a +108 ?C point charge has magnitude 4.00 N. How far apart are these two charges? (k = 1/4??0 = 8.99 × 109 N · m2/C2)

2. What is the magnitude of a the vertical electric field that will balance the weight of a plastic sphere of mass that has been charged to -3.0 nC? (k = 1/4??0 = 9.0 × 109 N · m2/C2)