The escape speed of an electron launched from the surface of a glass sphere of diameter $1\ cm$ that has been charged to $10\ nC$ is $x \times 10^7\ m/sec$ . The value of $x$ is
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$\frac{1}{2}m{v^2} = \frac{1}{{4\pi { \in _0}}}\frac{{Qe}}{R}$
$v = \sqrt {2\left( {\frac{1}{{4\pi { \in _0}}}} \right)\frac{{Qe}}{{m{R^2}}}} $
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