RAJASTHAN PMT Rajasthan - PMT Solved Paper-2003

  • question_answer
    In a capillary tube, water rises to a height of 2 cm. The height of water that will rise in another capillary tube of radius one-third that of first is               

    A)  2 cm                                     

    B)  3 cm          

    C)  6 cm                     

    D)         0.67 cm      

    Correct Answer: C

    Solution :

    If h is height of water raised in capillary tube of radius r, then according to  \[T=\frac{rhdg}{2\cos }\] rh = constant for same surface ten sin T, same density d  and same angle of contact \[\] \[\therefore \]  \[{{r}_{1}}{{h}_{1}}={{r}_{2}}{{h}_{2}}\] \[\Rightarrow \]               \[{{h}_{2}}=\frac{{{r}_{1}}{{h}_{1}}}{{{r}_{2}}}\]                                 (1) Here : \[{{h}_{1}}=2\,cm,\,{{r}_{2}}=\frac{{{r}_{1}}}{3}\] \[\Rightarrow \,\,\frac{{{r}_{1}}}{{{r}_{2}}}=3\] from eq. (1)               \[\therefore \]  \[{{h}_{2}}=3\times 2=6\,cm\]


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