Test: Types of Fluids - Mechanical Engineering MCQ

Explanation: When n = 1, the relation reduces to Newton’s law of viscosity: z = A * , where A will represent the viscosity of the fluid. The fluid following this relation will be a Newtonian fluid as it is a linear relation. The equation given is of a straight line.

Explanation: When n ≠ 1, the relation will be treated as Power law for Non-Newtonian fluids:
.
For n < 1, the rate of change of the shear stress decreases with the increase in the value of velocity gradient. Such fluids are called Pseudoplastics.

For n > 1, the rate of change of the shear stress increases with the increase in the value of velocity gradient. Such fluids are called Dilatants.

The relation between shear stress Z and velocity gradient  of a fluid is given by 
where A is the flow consistency index and n is the flow behaviour index.

Thus [A] will be independent of time when n = 2.

Explanation: For Bingham Plastics, shear stress will not remain constant after an yield value of stress. Thus, A ≠ 0;B ≠ 0. After the yield value, the relation between the shear stress and velocity gradient will become linear. Thus, n = 1.

Explanation: For Rheopectics, shear stress will not remain constant after an yield value of stress. Thus, A ≠ 0; B ≠ 0. After the yield value, the rate of change of the shear stress increases with the increase in the value of velocity gradient. Thus, n > 1.

Explanation: For Thixotropics,their viscosity is time dependent and decreases as time goes on.

Explanation:

• The graph corresponding to n = n₁ represents Pseudoplastics, for which the rate of change of the shear stress decreases with the increase in the value of velocity gradient.
• The graph corresponding to n = n₂ represents Newtonian fluids, for which shear stress changes linearly with the change in velocity gradient.
• The graph corresponding to n = n₃ represents Dilatents, for which the rate of change of the shear stress increases with the increase in the value of velocity gradient.

Explanation: Shear-thinning fluids are those which gets strained easily at high values of shear stresses. The relation between shear stress Z and velocity gradient   of a shear-thinning fluid is given by , where A and n are constants and n < 1. This relation is followed by Pseudoplastics.

Explanation: Shear-thickening fluids are those for which it gets harger to strain it at high values of shear stresses. The relation between shear stress Z and velocity gradient  of a shear-thickening fluid is given by   where A and n are constants and n > 1. This relation is followed by Dilatants.

Explanation: The relation between shear stress Z and velocity gradient  of a fluid is given by   where A is the flow consistency index and n is the flow behaviour index. If n = -1, A = Z * Unit of Z is N/m² and  is s^-1. Thus, the unit of A will be N/m² s.

Density of oil ρ_oil = 800 kg/m3
Density of water ρ_water = 1000 kg/m3
Density of air ρ_air = 1.16 kg/m3
Acceleration due to gravity g = 10 m/s2

PA – ρ_oil g (0.2) – ρ_air g (0.08) + ρ_water
g (0.38) = P_B
∴ PB – PA = 2.199 kPa

Hence, the correct answer is –2.2 kPa.

Density of helium

Under the equilibrium condition,
Buoyant force
= Weight of balloon + Weight of Helium
ρ_air  × (Volume of balloon) g
= W_balloon + ρ_Helium × (Vol. of balloon) g

Weight of balloon
= (ρ_air – ρ_Helium) × V_balloon × g

Density of Hg = = ρ × Hg 13 6 10 kg/m 3 3 .
Density of water = = ρ_H20
1000 kg/m³

Pressure above the section (1)–(1) should be same

Hence, the correct option is (a).

Gauge pressure inside the spherical droplet

= 

Gauge pressure inside the bubble

= 

where ‘d’ is the diameter of bubble and droplet
P_bubble = 2P_droplet
Hence, the correct option is (d).

Given that density of cube material δ_cube = 800 kg/m³

δ_water = 1000 kg/m3

weight of cube = δ_cube × volume of cube × g

= 800 × 0.1 × 0.1 × 0.1 × g

= 0.8 gN

To just lift the cube weight of cube = bouyamey force = weight of liquid displaced

= liquid × volume of liquid × g

= 1000 × 0.1 × 0.1 × h × g

= 10 hg where h = height of water pound

By equating weight of cube = bouyamey force

0.8g = 10 hg

h = 0.8/10 = 0.08m  = 80mm