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A small particle of mass m moves in such a way that the potential energy of particle is given as \mathrm{U}=-\frac{1}{2} \mathrm{~m} \alpha^2 \mathrm{r}^2where \alpha is constant and \mathrm{r} is the distance of particle from centre. If Bohr's model of quantization of angular momentum and circular orbit is valid for the particle. (\mathrm{h}= Planck's constant). Total energy of particle in its orbit is

Option: 1

-\frac{n h \alpha}{4 \pi}


Option: 2

\frac{\mathrm{nh} \alpha}{2 \pi}


Option: 3

zero


Option: 4

-\frac{\mathrm{nh} \alpha}{2 \pi}


Answers (1)

best_answer

\mathrm{F}=-\frac{\mathrm{dU}}{\mathrm{dr}}=\frac{\mathrm{mV}_{\mathrm{n}}^2}{\mathrm{r}_{\mathrm{n}}}

                m \alpha^2 r_n=\frac{m V_n^2}{r_n}                     (1)

              \text { and } \mathrm{mv}_{\mathrm{n}} \mathrm{r}_{\mathrm{n}}=\frac{\mathrm{nh}}{2 \pi}                    (2)

Solving equations (1) and (2)

\mathrm{r}_{\mathrm{n}}=\left(\frac{\mathrm{nh}}{2 \pi \mathrm{m \alpha}}\right)^{1 / 2}

\text { and } \mathrm{K}=\frac{1}{2} \mathrm{mv}_{\mathrm{n}}^2=\frac{\mathrm{nh} \alpha}{4 \pi}

\text { Total energy } \mathrm{E}=\mathrm{U}+\mathrm{K}=-\frac{1}{2} \mathrm{~m} \alpha^2 \mathrm{r}_{\mathrm{n}}^2+\frac{1}{2} \mathrm{mV}_{\mathrm{n}}^2=0

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shivangi.bhatnagar

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