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JCECE Engineering JCECE Engineering Solved Paper-2008

  • question_answer
    Spherical balls of radius \[R\] are falling in a viscous, fluid of viscosity \[\eta \] with a velocity\[v\]. The retarding viscous force acting on the spherical ball is

    A)  directly proportional to \[R\] but inversely proportional to\[v\]

    B)  directly proportional to both radius \[R\] and velocity\[v\]

    C)   inversely proportional to both radius \[R\] and velocity\[v\]

    D)   inversely proportional to \[R\] but directly proportional to velocity\[v\]

    Correct Answer: B

    Solution :

    Retarding force acting on a ball falling into a viscous fluid                 \[F=6\pi \eta Rv\] where           \[R=\]radius of ball,                 \[v=\] velocity of ball, and        \[\eta =\]coefficient of viscosity. \[\therefore \]  \[F\propto R\]and\[F\propto v\] Or in words, retarding force is directly proportional to both \[R\] and \[v\].


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