Question

Two charged particles having charge $1\mu C$ and $-1\mu C$ and of mass $50g$ each are held at rest while their separation is $2m$. Find the relative velocity of the particles when their separation is $0.5m$.

• A. $\frac{1}{5}m/s$
• B. $\frac{\sqrt{3}}{5}m/s$
• C. $\frac{3\sqrt{3}}{5}m/s$
• D. $\frac{3\sqrt{3}}{10}m/s$

Answer 1

Answer: (C)

Speed of both will be same at any time,
$(KE+PE{)}_f=(KE+PE{)}_i$
$2\left(\frac{1}{2}m{v}^2\right)-\frac{9\times 10^9\times 10^{-12}}{0.5}$
$=-\frac{9\times 10^9\times 10^{-12}}{2}+0$
$m{v}^2=9\times 10^{-3}\left[\frac{1}{0.5}-\frac{1}{2}\right]$
Putting $m=50/1000;v=\frac{3\sqrt{3}}{10}m/s$