Hello, everyone :-) We have a wooden sphere at a height of h = 1 m above the surface of the Earth which has a perimeter of RZ = 6 378 km and a weight of MZ = 5.97 · 10^24 kg. The sphere has a perimeter of r = 1 cm and is made of a wood which has the density of ρ = 550 kg·m − 3. Assume that the Earth has an electric charge of Q = 5 C. What is the charge q that the sphere has to have float above the surface of the Earth? How does this result depend on the height h? We can use Coulomb's and Newton's law. I can say the force of F = m_s*g = 4/3 * π * r^3 * ρ * g = the force of Coulomb's law 4/3*π*r^3*ρ*g = |Q_1|*|Q_2|/(4*π*e_0*e_1) |Q_1| = 4/3*π*r^3*ρ*g*4*π*e_0*e_1/|Q_2| Ok, this is my solution. Is it OK? Sorry for my bad English and thanks for advice.