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2. Electric Potential and Capacitance
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Mass of charge $Q$ is $m$ and mass of charge $2Q$ is $4\,m$ . If both are released from rest, then what will be $K.E.$ of $Q$ at infinite separation
A
$\frac{{8K{Q^2}}}{{5r}}$
B
$\frac{{4K{Q^2}}}{{5r}}$
C
$\frac{{K{Q^2}}}{{4r}}$
D
$\frac{{K{Q^2}}}{{2r}}$
Solution
$\frac{\left(\mathrm{K}_{\mathrm{f}}\right)_{\mathrm{Q}}}{\left(\mathrm{K}_{\mathrm{f}}\right)_{2 \mathrm{Q}}}=\frac{4 \mathrm{m}}{\mathrm{m}}=\frac{4}{1}$
$\Rightarrow \quad\left(\mathrm{K}_{\mathrm{f}}\right)_{\mathrm{Q}}=\frac{4}{5}\left[\frac{\mathrm{k}(2 \mathrm{Q})(\mathrm{Q})}{\mathrm{r}}\right]=\frac{8 \mathrm{k} \mathrm{Q}^{2}}{5 \mathrm{r}}$
Standard 12
Physics
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