Magnitude of Charge?

Question

Electrical Liftoff. A charge q is glued on top of you head and another like charge of equal magnitude is glued to the floor beneath your shoes. If you are 1.90m tall and have a mass of 70.0 kg, what magnitude charge q will make the normal force of the floor on you equal to zero?

Answer 1

Normal Force = mg = (kq^2)/(r^2) = Electric Force

= 70kg * 9.81m/s/s = (8.99*10^9 * q^2)/(1.9^2)

solving for q yields  0.000525 C