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Mass is suspended?
A 23.1-g mass is suspended 2.87 cm above a nonconducting flat plate, directly above an embedded charge of q.
a) If the mass has the same charge, q, how much must q be so that the mass levitates (just floats, neither rising nor falling)?
b) If the charge q is produced by adding electrons to the mass, by how much will the mass be changed?
2 Answers
- nyphdinmdLv 75 years agoFavorite Answer
The force of repulsion has to equal the force of gravity. Let h = 2.87 cm = 0.0287 m then
mg = kq^2/h^2 --> q = sqrt(mgh^2/(k)) = h*sqrt(mg/k) = 1.39x10^-7 coul
where m = 0.,0231 kg, k = 9*10^9 N-m^2/C^2
Number of electrons = q/(1.6x10^-19C) = 8.71x10^11 electrons
Mass increase = Number of electrons x mass of electrons = 8.71x10^11 * 9.11x10^-31 kg = 7.94x10^-19 kg
