## College Physics (4th Edition)

The charge on each sphere is $~-5.0\times 10^{-7}~C$
We can find the magnitude of the charge $q$ on each sphere: $F = \frac{k~q~q}{r^2}$ $q^2 = \frac{F~r^2}{k}$ $q = \sqrt{\frac{F~r^2}{k}}$ $q = \sqrt{\frac{(0.036~N)(0.25~m)^2}{9.0\times 10^9~N~m^2/C^2}}$ $q = 5.0\times 10^{-7}~C$ Since the magnitude of the charge on each sphere is $5.0\times 10^{-7}~C$ and the charge is negative, the charge on each sphere is $~-5.0\times 10^{-7}~C$