A particle is moving with uniform speed along the circumference of a circle of radius R under

Question:

A particle is moving with uniform speed along the circumference of a circle of radius $\mathrm{R}$ under the action of a central fictitious force $\mathrm{F}$ which is inversely proportional to $\mathrm{R}^{3}$. Its time period of revolution will be given by:

  1. (1) $\mathrm{T} \propto \mathrm{R}^{\frac{5}{2}}$

  2. (2) $\mathrm{T} \propto \mathrm{R}^{2}$

  3. (3) $\mathrm{T} \propto \mathrm{R}^{\frac{4}{3}}$

  4. (4) $\mathrm{T} \propto \mathrm{R}^{\frac{3}{2}}$


Correct Option: , 2

Solution:

(2)

$F \propto \frac{1}{R^{3}}$

$F=\frac{K}{R^{3}}$

$\frac{m v^{2}}{R}=\frac{K}{R^{3}}$

$m(\omega R)^{2}=\frac{K}{R^{2}}$

$m \omega^{2} R^{2}=\frac{K}{R^{2}}$

$\omega^{2}=\frac{K}{m}\left(\frac{1}{R^{4}}\right)$

$\left(\begin{array}{l}\frac{2 \pi}{T} \\ 2\end{array}\right)^{2} \frac{1}{R^{4}}$

$\frac{4 \pi^{2}}{T^{2}} \propto \frac{1}{R^{4}}$

$T \propto R^{2}$

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