Question

Find the coulombic force between two $\alpha -particles$ separated by a distance of $8.2$ fermi, in air.

• A. $10N$
• B. $11N$
• C. $14N$
• D. $24N$

Answer 1

The correct option is C $14N$

Each $\alpha -particle$ posses positive charge of $2e$

$e=1.6\times {10}^{-19}C$

$Q=2e$$R=8.2fermi=8.2\times 10^{-15}m$

$F=\frac{Q.Q}{4\pi {ϵ}_o{R}^2}$

$⟹F=\frac{4e^2}{4\pi {ϵ}_o{R}^2}$

$⟹F=\frac{9\times {10}^9\times 4\times {1.6}^2\times {10}^{-38}}{{8.2}^2\times {10}^{-30}}$

$⟹F=14N$

Answer-(C)