# Fluid Flow and Heat Transfer - 2 - MCQs with Answers

## Fluid Flow and Heat Transfer – 2 – MCQs with Answers

1. What is the correct formula for the shear stress (τ) in a flowing fluid according to the Newton's law of viscosity?

a. (τ) = (1 / μ) (du / dy)
b. (τ) = μ (du / dy)
c. (τ) = μ A (du / dy)
d. none of the above

Where,
μ = absolute viscosity of the flowing fluid
(du / dy) = change in velocity of a layer per unit change in distance of that layer from the surface
A = area of the surface on which the fluid is flowing

ANSWER: b. (τ) = μ (du / dy)

2. What is the SI unit for absolute or dynamic viscosity (μ)?

a. Ns/m2
b. Nm2/s
c. N/m2s
d. N/m2

3. What is the relation between the absolute viscosities of liquid and gas?

a. (μliquid) ≈ (μgas)
b. (μliquid) << (μgas)
c. (μliquid) >> (μgas)
d. none of the above

4. The viscosity of a liquid

a. increases with increase in liquid temperature
b. decreases with increase in liquid temperature
c. is not affected by the change in liquid temperature
d. is unpredictable

ANSWER: b. decreases with increase in liquid temperature

5. How is the viscosity of gas affected by change in its temperature?

a. viscosity of a gas decreases with increase in temperature of gas
b. viscosity of a gas increases with increase in temperature of gas
c. viscosity of a gas is not affected by change in temperature of gas
d. viscosity of a gas is unpredictable

ANSWER: b. viscosity of a gas increases with increase in temperature of gas

6. What is kinematics viscosity of a fluid?

a. dynamic viscosity per unit volume of the fluid
b. dynamic viscosity per unit weight of the fluid
c. dynamic viscosity per unit density of the fluid
d. none of the above