A cylindrical vessel containing a liquid is rotated about its axis

Question:

A cylindrical vessel containing a liquid is rotated about its axis so that the liquid rises at its sides as shown in the figure. The radius of vessel is $5 \mathrm{~cm}$ and the angular speed of rotation is $\omega \mathrm{rad} \mathrm{s}^{-1}$. The difference in the height, $\mathrm{h}($ in $\mathrm{cm})$ of liquid at the centre of vessel and at the side will be:

 

  1. $\frac{25 \omega^{2}}{2 g}$

  2. $\frac{2 \omega^{2}}{5 g}$

  3. $\frac{5 \omega^{2}}{2 g}$

  4. $\frac{2 \omega^{2}}{25 \mathrm{~g}}$


Correct Option: , 4

Solution:

Applying pressure equation from A to B

$\mathrm{P}_{0}+\rho \cdot \frac{\mathrm{R} \omega^{2}}{2} \cdot \mathrm{R}-\rho g h=\mathrm{P}_{0}$

$\frac{\rho R^{2} \omega^{2}}{2}=\rho g h$

$\mathrm{h}=\frac{\mathrm{R}^{2} \omega^{2}}{2 \mathrm{~g}}=(5)^{2} \frac{\omega^{2}}{2 \mathrm{~g}}=\frac{25}{2} \frac{\omega^{2}}{\mathrm{~g}}$

 

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