# NEET Questions Solved

PMT - 2003

An electron is moving round the nucleus of a hydrogen atom in a circular orbit of radius r. The coulomb force $\stackrel{\to }{F}$ between the two is (Where $K=\frac{1}{4\pi {\epsilon }_{0}}$)

(1) $-K\frac{{e}^{2}}{{r}^{3}}\stackrel{^}{r}$

(2) $K\frac{{e}^{2}}{{r}^{3}}\stackrel{\to }{r}$

(3) $-K\frac{{e}^{2}}{{r}^{3}}\stackrel{\to }{r}$

(4) $K\frac{{e}^{2}}{{r}^{2}}\stackrel{^}{r}$

(3) $\stackrel{\to }{F\text{\hspace{0.17em}}}=-\text{\hspace{0.17em}}k\frac{{e}^{2}}{{r}^{2}}\stackrel{^}{r}=-\text{\hspace{0.17em}}k.\frac{{e}^{2}}{{r}^{3}}\stackrel{\to }{r\text{\hspace{0.17em}}}$    $\left(\because \text{\hspace{0.17em}\hspace{0.17em}}\stackrel{^}{r}=\frac{\stackrel{\to }{r\text{\hspace{0.17em}}}}{r}\right)$

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