Force Example
SF = ma becomes ke2/r2 = m(v2/r), or
[{9x109 * (1.6x10-19)2} / {9.1x10-31 * 1x10-10}]1/2 =
Note that we took the + and - signs for the charges into account when we determined that the electric force was attractive and directed towards the center. The magnitude has to be considered as positive.