Question

The viscous force between the layers of a liquid does NOT depend on which of the following?
1. Contact area of the layers
2. Nature of the liquid
3. Velocity gradient
4. Density of the liquid 

Answer 1

Correct Answer - Option 4 : Density of the liquid 

CONCEPT:

• Viscosity is the property of the liquid due to which it opposes the relative motion between the layers of the liquid.
• Viscous force is the resistive force that is acting between the layers of liquid and opposes the relative motion between the layers and is given by

\(\Rightarrow F = -η A \frac{dV}{dx}\)

Where η = Coefficient of viscosity, A = Area, and \(\frac{dV}{dx} = Velocity \ gradient \)

• In the SI system of units, viscosity is measured in Pascal second, and in the CGS system of units, it is measured in Poise.

EXPLANATION :

• The viscous force acting between the layers of the liquid is given by

\(\Rightarrow F = -η A \frac{dV}{dx}\)

• From the above equation, it is clear that the frictional force depends on the following factors

1. Area
2. Coefficient of viscosity
3. Velocity gradient

• From the above discussion, it is clear that the viscous force depends on the velocity gradient i.e., the viscous force will depend on the velocity of the liquid.
• The viscous force also depends on the nature of the liquid. If the intermolecular force is high then the liquid has more viscosity or vice versa.
• The viscous force will not be depending on the density of the liquid
• Hence, option 4 is the answer