Engineering Physics Multiple Choice Questions on “Streamline and Turbulent Flow”.
1. A metal plate 5cm×5cm rest on a layer of castor oil 1mm thick whose coefficient of viscosity is 1.55Nsm(-2). Find the horizontal force required to move the plate with a speed of 2 cms(-1).
a) 0.775N
b) 0.0577N
c) 0.0775N
d) 0.577N
Answer: c
Clarification: F=ȠA dv/dx
F=1.55×25×10-4×(2×10-2)/(1×10-3)=0.0775N.
2. At what speed will the velocity head of stream of water be 40 cm?
a) 2.80cms-1
b) 280 cms-1
c) 28 cms-1
d) 0.280 cms-1
Answer: b
Clarification: h=v2/2g
v=√2gh=√(2×980×40)=280cms-1.
3. It is easier to cut an apple with a blunt knife than a sharp knife.
a) True
b) False
Answer: b
Clarification: The area of a sharp edge is much less than the area of a blunt edge. For the same total force, the effective force per unit area is more for the sharp edge than the blunt one. Hence a sharp knife cuts easily than a blunt knife.
4. It is easier to swim in sea water than in river water.
a) True
b) False
Answer: a
Clarification: The sea water has many salts dissolved in it. So the density of sea water is greater than that of river water. Consequently, the sea water exerts greater upthrust on the swimmer than the river water. Hence it is easier to swim in sea water than in river water.
5. If there were no gravity, which of the following will not be there for a fluid?
a) Viscosity
b) Surface tension
c) Pressure
d) Archimedes’ upward thrust
Answer: d
Clarification: Archimedes’ upward thrust will be absent for a fluid if there were no gravity.
6. Motion of a liquid in a tube is best described by ___________
a) Bernoulli theorem
b) Poiseuille’s equation
c) Stoke’s law
d) Archimedes’ principle
Answer: b
Clarification: Poiseuille’s formula gives the volume of a liquid flowing out per second through a horizontal capillary tube of length l, radius r, under a pressure difference p applied across its ends.
Q=V/t=(πpr4)/8Ƞl.
7. Critical velocity of the liquid ___________
a) Decrease when radius decreases
b) Increases when radius increases
c) Decreased when density increases
d) Increases when density increases
Answer: c
Clarification:
vc=(Re Ƞ)/pD
Critically velocity decreases when density ρ increases or diameter D increases.
8. A steel ball is dropped in oil, then ___________
a) The ball attains constant velocity after sometime
b) The ball stops
c) The speed of ball will keep on increasing
d) The speed of the ball will decrease
Answer: a
Clarification: The ball attains constant velocity after falling through some distance in oil when the weight of ball gets balanced by upthrust and the upward viscous force.
9. An aeroplane gets its upward lift due to a phenomenon described by the ___________
a) Archimedes’ principle
b) Bernoulli’s principle
c) Buoyancy principle
d) Pascal law
Answer: b
Clarification: An aeroplane gets dynamic upward lift in accordance with Bernoulli’s principle.
10. The rate of flow of liquid through an orifice of a tank does not depend upon ___________
a) The size of the orifice
b) Density of liquid
c) The height of fluid column
d) Acceleration due to gravity