Question

Find the electric force between two protons separated by a distance of 1 fermi (1 fermi = 10⁻¹⁵ m). The protons in a nucleus remain at a separation of this order.

Answer 1

We know:
Charge on a proton, q = 1.6 × 10⁻¹⁹ C
Given, separation between the charges, r = 10⁻¹⁵ m
By Coulomb's Law, electrostatic force,
$F=\frac{1}{4\mathrm{\pi }{\epsilon }_0}\frac{q_1{q}_2}{r^2}$
$$\begin{gathered} \Rightarrow F=9\times {10}^9\times \frac{{\left(1.6\times {10}^{-19}\right)}^2}{{\left({10}^{-15}\right)}^2} \\ \Rightarrow F=230\mathrm{N} \end{gathered}$$