A magician decides to use an electric field to levitate a light plastic ball in the air. The ball has a mass of 15 grams and can be given a charge of +0.5 coulombs.
A: Calculate the weight of the ball
B: Determine the strength & direction of the external electric field that the magician would require to levitate the ball.

Question

A magician decides to use an electric field to levitate a light plastic ball in the air. The ball has a mass of 15 grams and can be given a charge of +0.5 coulombs.
A: Calculate the weight of the ball
B: Determine the strength & direction of the external electric field that the magician would require to levitate the ball.

anonymous · Answer

sorry?

ghazi · Answer

see, to lift the ball in the air you need to balance weight of ball with that of force produced by electric field on charges therefore 
$$force= charge*E=m*g$$ now you can calculate m, and for weight you just use m*g= q*E

ghazi · Answer

if you're talking about strength then use gauss law over the surface of sphere to find out electric flux density (strength) and obviously direction should be upward so as to lift the ball since weight of ball acts towards gravity (that is downwards)