AMU Medical AMU Solved Paper-2009

  • question_answer
    A capillary tube of radius r is immersed in water and water rises in it to a height h. The mass of water in the capillary tube is 5 g. Another capillary tube of radius 2r is immersed in water. The mass of water that will rise in this tube is

    A)  2.5 g                                     

    B)  5.0 g

    C)  10 g                                      

    D)  20 g

    Correct Answer: C

    Solution :

                     When one end of capillary tube of radius r is immersed into a liquid of density p, to maintain the equilibrium the liquid level rises in the capillary tube upto height                                 \[h=\frac{2T\cos \theta }{\rho rh}\]  Mass of the water in first tube is                 \[m=\pi {{r}^{2}}h\rho \]                 \[=\pi {{r}^{2}}\left[ \frac{2T\,\cos \theta }{\rho rg} \right]\times \rho \]                 \[m=\frac{\pi r(2T\,\cos \theta )}{g}\] or \[m\propto r\] Similarly for second tube                 \[m\propto r\] or            \[\frac{m}{m}=\frac{r}{r}=\frac{r}{2r}=\frac{1}{2}\] or            \[m=2m=2\times 5=10\,g\]


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