Q129 / 155 · WBJEE 2019 · Physics

A small spherical body of radius $r$ and density p moves with the terminal velocity $v$ in a fluid of coefficient of viscosity $\eta$ and density $\bar{\sigma}$. What will be the net force on the body?

  • A
    $\frac{4 \pi}{3} r^{3}(p-\sigma) g$
  • B
    $6 \pi \eta rv$
  • Correct answer
    C
    Zero
  • D
    Infinity

Solution

When the spherical body falls with constant velocity, i.e. terminal velocity then the net force becomes zero, i.e the weight of body is equal to the buoyancy force. Hence, $F_{\text {net }}=0$

Hence, the correct answer is option: 'C'.

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