Fluid Mechanics Interview Questions and Answers on “Fluid Properties – 2”.
1. Calculate the specific weight and weight of 20dm3 of petrol of specific gravity 0.6.
a) 5886,117.2
b) 5886,234.2
c) 11772,117.2
d) None of the mentioned
Answer: a
Clarification: Specific weight = density*acceleration due to gravity
=.6*1000*9.81=5886N/m3
Weight=volume*specific weight
=5886*0.02=117.2N.
2. If 200m3 of fluid has a weight of 1060N measured on the planet having acceleration due to gravity 6.625m/s2, what will be it’s specific volume?
a) 0.8
b) 0.7
c) 0.9
d) 0.5
Answer: a
Clarification: Specific weight=Weight/volume
= (Mass*acceleration due to gravity)/volume
=density*acceleration due to gravity
=1/(specific volume *acceleration due to gravity)
Specific volume=1060/(200*6.625).
3. For an incompressible fluid does density vary with temperature and pressure?
a) It varies for all temperature and pressure range
b) It remains constant
c) It varies only for lower values of temperature and pressure
d) It varies only for higher values of temperature and pressure
Answer: b
Clarification: For an incompressible fluid, the change in density is negligible. Thus it does not change with temperature and pressure.
4. Specific gravity is what kind of property?
a) Intensive
b) Extensive
c) None of the mentioned
d) It depends on external conditions
Answer: a
Clarification: It is independent of quantity of matter present.
5. If there is bucket full of oil and bucket full of water and you are asked to lift them, which one of the two will require more effort given that volume of buckets remains same?
a) Oil bucket
b) Water bucket
c) Equal effort will be required to lift both of them
d) None of the mentioned
Answer: b
Clarification: Density of water is more that oil. Hence, its weight for same volume of oil will also be higher. Therefore, more effort will be required.
6. If the fluid has specific weight of 10N/m3 for a volume of 100dm3 on a planet which is having acceleration due to gravity 20m/s2 , what will be its specific weight on a planet having acceleration due to gravity 4m/s2?
a) 5 N/m3
b) 50 N/m3
c) 2 N/m3
d) 10 N/m3
Answer: c
Clarification: For same volume, specific weight is directly proportional to acceleration due to gravity
Specific weight=4*10/20=2.
7. Should Specific Wieght of incompressible fluid only be taken at STP?
a) Yes, as specific weight may show large variation with temperature and pressure
b) No, it can be taken for any temperature and pressure
c) It should be taken at standard temperature but pressure may be any value
d) It should be taken at standard pressure but temperature may be any value
Answer: b
Clarification: Specific weight is inversely proportional to volume. For incompressible fluid , variation of volume with temperature and pressure is negligible for practical consideration. Therefore, specific weight remains constant.
8. An instrument with air as fluid was involved in some experiment( specific volume was the characteristic property utilized) which was conducted during day in desert. Due to some reason experiment couldn’t be conducted during day and had to be conducted during night. However there were considerable errors in obtained values. What might be the reason of these errors?
a) It was human error
b) It was instrumental error
c) Error was due to the fact that experiment was conducted at night
d) None of the mentioned