NEET Sample Paper NEET Sample Test Paper-47

  • question_answer
    Two metals spheres are falling through a liquid of density \[2\times 1{{0}^{3}} kg / {{m}^{3}}\]with the same uniform speed. The material density of sphere 1 and sphere\[2 are\,\,8\times {{10}^{3}}kg/{{m}^{3}} and 11\times 1{{0}^{3}} kg/{{m}^{3}}\] respectively. The ratio of their radii is:

    A) \[\frac{11}{8}\]                         

    B) \[\sqrt{\frac{11}{8}}\] 

    C) \[\frac{3}{2}\]                          

    D) \[\sqrt{\frac{3}{2}}\]

    Correct Answer: D

    Solution :

    Terminal velocity \[{{\operatorname{V}}_{{{T}_{1}}}}=\frac{2}{9}\frac{\left( \sigma -\ell  \right)}{\eta }{{\operatorname{r}}_{1}}^{2}\] \[{{\operatorname{V}}_{{{T}_{2}}}}=\frac{2}{9}\frac{\left( {{\sigma }_{2}}-\ell  \right)}{\eta }{{\operatorname{r}}_{2}}^{2}\] \[{{\operatorname{V}}_{{{T}_{2}}}}={{V}_{{{T}_{2}}}}\] \[\frac{2}{9}\frac{\left( 8\times {{10}^{3}}-2\times {{10}^{3}} \right)}{\eta }{{\operatorname{r}}_{1}}^{2}=\frac{2}{9}\frac{\left( 11\times {{10}^{3}}-2\times {{10}^{3}} \right)}{\eta }{{\operatorname{r}}_{2}}^{2}\]\[6\times 1{{0}^{3}}{{r}_{1}}^{2}=9\times 1{{0}^{3}}{{r}_{2}}^{2}\] \[\frac{{{r}_{1}}}{{{r}_{2}}}=\sqrt{\frac{3}{2}}\]


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