Question

The viscous drag on a spherical body moving with a speed V is proportional to:
(A) $\sqrt V $
(B) $V$
(C) $\dfrac{1}{{\sqrt V }}$
(D) ${V^2}$

Answer 1

Hint: To answer this question we should be knowing the formula to find the viscous drag. The formula of viscous drag is given as a relation between viscosity, radius and the velocity. Which among the mentioned expressions of velocity is proportional to viscosity can be determined from the formula.

Complete step by step answer:
The formula to find the viscous drag on a spherical body moving with a speed V, as given in the question will be:
$F = 6\pi nrV$
In this case,
F denotes the viscous drag on the spherical body which is moving
R is the radius
n denotes the viscosity and
V is the velocity.
So from the above mentioned formula it is clear that the viscous drag on a spherical body moving with a speed V is proportional to V.

Hence the correct answer is Option B.

Note: We have come across the term viscosity in the answer. For a better understanding we have to understand the meaning of viscosity. Viscosity is defined as the measurement of the resistance of a fluid to its flow. This situation indirectly describes the internal friction of the liquid. This is the resistance which is formed because of the molecular structure of the liquid.
In the question we have come across another term which is viscous drag. We need to define that too for better understanding. By viscous drag we mean the resistive force that is exerted on an object which is in motion. This force depends on the velocity of the terminal speed.