1. The problem statement, all variables and given/known data A 3.0mm-diameter copper ball is charged to 50nC.What fraction of its electrons have been removed? The density of copper is 8900kgm^3. 2. Relevant equations d=m/v; v=4/3* pi r^3 3. The attempt at a solution I worked through it and got 5.682 E -16, but that answer was wrong. I first found the number of electrons were in it (3.125 E 11). I then found the volume (1.414 E -8), and I think that's where I got stuck after that.