## Conceptual Physics (12th Edition)

Use Newton's Law of gravity, $F = G \frac{m_{1} \; m_{2}}{d^{2}}$. Using the values for G, electron mass, proton mass, and distance that are given, we find $F = 1.0 \times 10^{-47} N$. Use Coulomb's Law, $F = k \frac{q_{1} \; q_{2}}{d^{2}}$. Using the values for k, electron charge, proton charge, and distance that are given, we find $F = 2.3 \times 10^{-8} N$. The electrical attraction is more than $10^{39}$ = 1,000,000,000,000,000,000,000,000,000,000,000,000,000 times greater than the gravitational attraction, justifying the neglect of gravity.