AMU Medical AMU Solved Paper-2001

  • question_answer
    A rain drop of radius 0.3 mm has a terminal velocity of 1 m/s in air. The viscosity of air is \[\text{18}\times \text{1}{{0}^{-5}}\] poise. The viscous force on the drop is

    A)  \[16.95\times 10\]                         

    B)  \[1.695\times {{10}^{-2}}\]

    C)  \[\text{1}.0\text{17}\times \text{1}{{0}^{-\text{11}}}\text{ N}\]             

    D)  \[\text{1}0\text{1}.\text{73}\times \text{1}{{0}^{-\text{9}}}\text{ N}\]

    Correct Answer: D

    Solution :

                     From Stokes formula                 \[F=6\pi \eta \,rv\] Given,   \[\eta =18\times {{10}^{-5}}=18\times {{10}^{-6}}\] kg/mass,                 r = 0.3 mm                 \[=0.3\times {{10}^{-3}}m\],                 v = 1 m/s \[\therefore \]  \[F=6\times 3.14\times 18\times {{10}^{6}}\times 0.3\times {{10}^{-3}}\times 1\] \[\Rightarrow \]               \[F=101.73\times {{10}^{-9}}N\]


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