Test: Properties of Fluids - 2 - Mechanical Engineering MCQ

D₂ = 100 mm

V = 10 m/s

μ = 0.1 kg/m ∙ s

L = 100 mm (assume)

Frictional force = shear stress × surface area

According to Newton's law of viscosity, shear stress is directly proportional to the rate of angular deformation (shear strain) or velocity gradient across the flow.

Width of flat plate L = 1 m

Velocity of flat plate U = 0.01 m/s

Distance between flat plate and wall d = 0.1 m

If we assume the length of plate be Z

Rates of mass through plate = Rate of mass displaced between plates and wall.
LZ × dh = 2 × U_avg × d × Zdt

Where U_avg is the average velocity of the fluid (in m/s) draining out at the instant

LZdh = 2 × U_avg × d × zdt

Hence, the correct answer is 0.05 m/s.

The correct option is 4. A real fluid is a fluid that has viscosity, which means it resists shear or tensile stress and exhibits a continuous deformation when subjected to an external force. Real fluids may have variable viscosity and density, and they can also be compressible. Surface tension is a property of liquids and is not present in all fluids. Therefore, option 1 is incorrect. Zero shear stress is not a characteristic of real fluids, making option 2 incorrect. While real fluids may have constant viscosity and density under certain conditions, it is not a necessary characteristic, making option 3 incorrect.

A fluid is a substance that deformed continuously when shear stress is applied to it irrespective of the magnitude of the shear stress. Because of the continuous deformation flow of the liquid can be seen. In other words, we can also tell that liquid can not sustain any shear load.

Ideal Fluid: A fluid, which is incompressible and is having no viscosity is known as ideai fluid. Ideal fluid is only an imaginary fluid as all the fluids, which exists have some viscosity.

Mass m = 2 kg

Acceleration g = 10 m/s²

Height h = 15 mm

Terminal velocity V = ?
We know that terminal velocity is constant velocity, therefore net acceleration is zero.
Shear force due to oil film = weight of block

Hence, the correct answer is 10.714.
but upto 1 decimal place 10.7

• Surface tension, in simple words, is defined as the force exerted on the fluid particles on a surface per unit length in the plane of the liquid surface perpendicular to either side of an imaginary line drawn to the surface.
• Mathematically, surface tension is expressed as the ratio of force to length. It is the or type of behavior of the liquid surface to contract into a minimum surface area. The standard unit of surface tension is N m^-1. 

Newton's law of viscosity:

• Viscosity is a property of fluid by virtue of which they offer resistance to shear or angular deformation.
• It is primarily due to cohesion and molecular momentum exchange between fluid layers, and as flow occurs, these effects appears as shearing stresses between the moving layers.
• According to Newton's law of viscosity, shear stress is directly proportional to the rate of angular deformation (shear strain rate) or velocity gradient across the flow.

where, τ = shear stress

μ = absolute or dynamic viscosity

⇒  du/dy = velocity gradient 

⇒ dα/dt = rate of angular deformation (shear strain)

γ = 7.4 × 10⁻⁷ m²/s

SG = 0.88
ρ = (SG) × ρ_water = 0.88 × 1000

= 880 kg/m³

du = u₂ – u = 0.5 m/s

μ = γρ

= 0.651 Pa

Hence, the correct option is (b).

The fluid which obeys the Newton’s law of viscosity is known as Newtonion fluid e.g.: Air, water, Kerosene.

In the expression: 

If n < 1, B = 0
then it is known as pseudo plastic

Surface tension a line force caused by cohesion of fluid particle at the surface, the property of cohesion enables a liquid to resist tensile stress.

As kinematic viscosity of gas is the function of temperature, which is given by

The increase in temperature does not affect the viscosity very much because the values of α, β are very less. So, increase of temperature does not increase the viscosity very much.
Hence, the correct option is (a).