MCQs on Viscosity
1 - Question
Viscosity is defined as the external resistance offered by a fluid to change its shape or relative motion of its parts.
a) Yes
b) It is internal resisting force
c) It is not offered but exerted on the fluids
d) None of the listed
View Answer
Answer: b
Explanation: It is an internal resisting force.
2 - Question
Stream line flow happens when intermediate layers move with velocities proportional to the square of distance from the stationary plate.
a) True
b) False
View Answer
Answer: b
Explanation: It is proportional to distance and not square of it.
3 - Question
Newton law of viscosity states that shear stress is proportional to rate of shear at any point in the fluid.
a) True
b) False
View Answer
Answer: a
Explanation: P/A proportional to U/h.
4 - Question
Calculate the kinematic viscosity if Saybolt viscosity is 400cSt.
a) 400SUS
b) 40.25SUS
c) 86.32SUS
d) 87.55SUS
View Answer
Answer: d
Explanation: z=0.22t-[180/t] where t=400.
5 - Question
Viscosity of lubricating oil decrease with increasing temperature.
a) Yes
b) It increases linearly
c) It increases hyperbolically
d) it remains constant
View Answer
Answer: a
Explanation: Intermolecular forces decrease on the increase of temperature.
6 - Question
Which of the following lubricant has least rate of change of viscosity w.r.t temperature.
a) VI=20
b) VI=30
c) VI=40
d) VI=50
View Answer
Answer: d
Explanation: Greater the VI, lesser is the rate of change w.r.t temperature.
7 - Question
Which of the following are not true for petroff’s equation?
a) Shaft is considered concentric with the bearing
b) Bearing is subjected to light load
c) Is used to find coefficient of friction
d) Frictional torque is given by fpr²l
View Answer
Answer: d
Explanation: M=fWr=f(2prl)r, W=projected area of bearing x pressure.
8 - Question
In hydrodynamic lubrication, film thickness remains unaffected by change in speeds.
a) True
b) Increase with increase in speed
c) Decrease with increase in speed
d) Disappear as the speed tends to infinty
View Answer
Answer: b
Explanation: As speed increases more and more lubricant is forces and pressure builds up thus separating the two surfaces. There is transition from thin film thick film.
9 - Question
For a hydrostatic thrust bearing, Thrust load=450kN, shaft speed=730rpm, shaft diameter=450mm, recess diameter=310mm, film thickness=0.15mm, viscosity of lubricant=160SUS and specific gravity=0.86. Calculate supply pressure
a) 10.2Pa
b) 4.01Pa
c) 4.01Mpa
d) 10.2Mpa
View Answer
Answer: c
Explanation: P=2Wln(225/155)/[π(225²-155²)] N/mm².
10 - Question
For a hydrostatic thrust bearing, Thrust load=450kN, shaft speed=730rpm, shaft diameter=450mm, recess diameter=310mm, film thickness=0.15mm, viscosity of lubricant=160SUS and specific gravity=0.86. Calculate flow requirement
a) 0.89l/s
b) 38.94l/min
c) 28.8l/min
d) None of the mentioned
View Answer
Answer: b
Explanation: Q=πPhᵌ/6µln(225/155) whereµ=z/10⁹ and z=0.86x[0.22×160-180/160]. µ=29.3 x 10¯⁹N-s/mm².
11 - Question
For a hydrostatic thrust bearing, Thrust load=450kN, shaft speed=730rpm, shaft diameter=450mm, recess diameter=310mm,film thickness=0.15mm,viscosity of lubricant=160SUS and specific gravity=0.86. Calculate power loss in pumping.
a) 2.68kW
b) 3.35kW
c) 2.6kW
d) 4.2kW
View Answer
Answer: c
Explanation: kW=Q(P-0)x10¯⁶.
12 - Question
For a hydrostatic thrust bearing, Thrust load=450kN, shaft speed=730rpm, shaft diameter=450mm, recess diameter=310mm,film thickness=0.15mm,viscosity of lubricant=160SUS and specific gravity=0.86. Calculate frictional power loss.
a) None of the listed
b) 2.3kW
c) 3.56kW
d) 4.2kW
View Answer
Answer: c
Explanation: kW=µn²(225⁴-155⁴)/hx58.05×10⁶.