What electric field strength will cause the bead to hang suspended in the air?

[cemar.]

1. A 0.180g plastic bead is charged by the addition of 0.700 x 10^10 excess electrons. What electric field strength will cause the bead to hang suspended in the air?



2. Is amount of excess electrons the exact same as the charge of the bead??



3. I am sure you use F=qE. But I am pretty stuck at the rest of it. I am sure there is a formula or soemthing i missed in lecture considering my prof is a little loopy.

 

[nicksauce]

Set qE = mg. q is the charge of 0.7 * 10^10 electrons, m is the mass of the bead, g is acceleration due to gravity. Shouldn't be too hard.