## College Physics (4th Edition)

The ratio of the electric force to the gravitational force is $~2.3\times 10^{39}$
We can find the electric force: $F = \frac{k~q_p~q_e}{r^2}$ $F = \frac{(9.0\times 10^9~N~m^2/C^2)~(1.6\times 10^{-19}~C)(-1.6\times 10^{-19}~C)}{(5.3\times 10^{-11}~m)^2}$ $F = -8.2\times 10^{-8}~N$ We can find the gravitational force: $F = \frac{G~m_p~m_e}{r^2}$ $F = \frac{(6.67\times 10^{-11}~N~m^2/kg^2)~(1.67\times 10^{-27}~kg)(9.1\times 10^{-31}~kg)}{(5.3\times 10^{-11}~m)^2}$ $F = 3.6\times 10^{-47}~N$ We can find the ratio of the magnitude of the electric force to the gravitational force: $\frac{8.2\times 10^{-8}~N}{3.6\times 10^{-47}~N} = 2.3\times 10^{39}$