How does the viscosity of fluids vary with increase in temperature?

Decreases for both liquids and gases

Increases for both liquids and gases

Increases for liquids, decreases for gases

Increases for gases, decreases for liquids

Decreases for both liquids and gases

Newton’s law of viscosity states that:

Shear stress is directly proportional to the shear strain

Shear stress is directly proportional to the viscosity

Shear stress is directly proportional to the velocity

Shear stress is directly proportional to the velocity gradient

A disc of radius R rotates at an angular velocity Ω inside a disc shaped container filled with oil of viscosity μ, as shown in figure. Assuming a linear velocity profile and neglecting shear stress on the outer disc edges, the formula for viscous torque on the disc is

\(\frac{{\pi \mu {\rm{\Omega }}{R^2}}}{h}\)

\(\frac{{\pi \mu {\rm{\Omega }}{R^5}}}{h^2}\)

\(\frac{{\pi \mu {\rm{\Omega }}{R^4}}}{h}\)

A fluid near a solid wall has an approximated velocity profile given by \(u\left( y \right) = \;{U_\infty } \times \sin \left( {\frac{{\pi y}}{{2\delta }}} \right),\;0 \le y \le \delta \) . The walls shear stress is given by:

\({\tau _{wall}} = \;\frac{{3\pi \mu {U_\infty }}}{{\delta }}\)

\({\tau _{wall}} = \;\frac{{\pi \mu {U_\infty }}}{{2\delta }}\)

\({\tau _{wall}} = \;\frac{{3\pi \mu {U_\infty }}}{{\delta }}\)

\({\tau _{wall}} = \;\frac{{2\pi \mu {U_\infty }}}{{\delta }}\)

\({\tau _{wall}} = \;\frac{{\pi \mu {U_\infty }}}{{\delta }}\)

has no viscosity and incompressible

If angle of contact of a drop of liquid is acute, then

Both adhesion and cohesion have no connection with angle of contact

In a capillary tube, the weight of the liquid raised is supported by:

vertical component of surface tension

Dynamic viscosity of the gas

Increases as temperature decreases

Increases as temperature increases

May increases or decreases with increases in temperature, depending on the nature of gas

For a Newtonian fluid

rate of shear stress is proportional to rate of shear strain

shear stress is proportional to shear strain

rate of shear stress is proportional to shear strain

shear stress is proportional to rate of shear strain

rate of shear stress is proportional to rate of shear strain

Kinematic viscosity is the ratio of:

Density of liquid to absolute viscosity

Absolute viscosity to density of liquid

Density of liquid to absolute viscosity

Mass of liquid to absolute viscosity

Absolute viscosity to mass of the liquid

Cavitation parameter is defined by

\(\frac{{{P_v} - P}}{{\frac{{p{V^2}}}{2}}}\)

\(\frac{{{P_{atm}} - {P_v}}}{{\frac{{p{V^2}}}{2}}}\)

\(\frac{{P - {P_{atm}}}}{{\frac{{\rho {V^2}}}{2}}}\)

\(\frac{{P - {P_v}}}{{\frac{{\rho {V^2}}}{2}}}\)

For Newtonian fluid behaviour, the shear stress exerted by the fluid is equal to the _______.

Fluid viscosity divided by the velocity gradient parallel to the direction of shear

Fluid viscosity divided by the velocity gradient perpendicular to the direction of shear

A product of the fluid viscosity and the velocity gradient parallel to the direction of shear

Product of the fluid viscosity and the velocity gradient perpendicular to the direction of shear

For liquids, the values of dynamic viscosity (μ) and kinematic viscosity (ν) are

Practically independent of variation of temperature

Highly dependent of variation of pressure

Practically independent of variation of pressure

Practically independent of variation of temperature

Increases with increase in temperature

one which obeys perfect gas laws

incompressible and frictionless

one which obeys perfect gas laws

Newton's law of viscosity depends upon

shear stress, pressure and velocity

shear stress and strain in the fluid

shear stress and rate of strain

In order to prevent the capillary action from affecting the column of liquid in a piezometer the diameter of the glass tube should be

more than 3 mm but less than 5 mm

For the hydrostatic pressure measurement in fluids at rest

The shear stress is zero only on horizontal plane

The shear stress depends upon the coefficient of viscocity

The shear stress is maximum on a plane inclined 45° to horizontal

The shear stress is zero only on horizontal plane

Pick the correct statement about viscosity.

In general, it decreases with temperature for gases because the internal force of attraction between two fluid layers gets decreased.

In general, it decreases with temperature for liquids because the internal force of attraction between two fluid layers gets decreased.

In general, it decreases with temperature for gases because the internal force of attraction between two fluid layers gets decreased.

In general, it increases with temperature for liquids because the internal force of attraction between two fluid layers gets increased.

In general, it increases with temperature for gases because the internal force of attraction between two fluid layers gets increased.

52 + Mcqs in Properties Of Fluids in Fluid Mechanics Page 1 McqOptions

1.	How does the viscosity of fluids vary with increase in temperature?
A.	Increases for both liquids and gases
B.	Increases for liquids, decreases for gases
C.	Increases for gases, decreases for liquids
D.	Decreases for both liquids and gases
Answer» D. Decreases for both liquids and gases

Discussion

2.	An increase in pressure of a liquid from 7.5 MPa to 15 MPa results into 0.2 percent decrease in its volume. The coefficient of compressibility of the liquid in m2/N is
A.	0.267 × 10-9
B.	2.67 × 10-9
C.	1 × 10-9
D.	None of the above
Answer» B. 2.67 × 10-9

Discussion

3.	A liquid compressed in cylinder has a volume of 0.04 m3 at 50 kg/cm2 and a volume of 0.039 m3 at 150 kg/cm2. The bulk modulus of liquid is
A.	400 kg/cm2
B.	4000 kg/cm2
C.	40 × 105 kg/cm2
D.	40 × 106 kg/cm2
Answer» C. 40 × 105 kg/cm2

Discussion

4.	Newton’s law of viscosity states that:
A.	Shear stress is directly proportional to the shear strain
B.	Shear stress is directly proportional to the viscosity
C.	Shear stress is directly proportional to the velocity
D.	Shear stress is directly proportional to the velocity gradient
Answer» E.

Discussion

5.	A disc of radius R rotates at an angular velocity Ω inside a disc shaped container filled with oil of viscosity μ, as shown in figure. Assuming a linear velocity profile and neglecting shear stress on the outer disc edges, the formula for viscous torque on the disc is
A.	\(\frac{{\pi \mu {\rm{\Omega }}{R^2}}}{h}\)
B.	πμΩhR3
C.	\(\frac{{\pi \mu {\rm{\Omega }}{R^5}}}{h^2}\)
D.	\(\frac{{\pi \mu {\rm{\Omega }}{R^4}}}{h}\)
Answer» E.

Discussion

6.	A fluid near a solid wall has an approximated velocity profile given by \(u\left( y \right) = \;{U_\infty } \times \sin \left( {\frac{{\pi y}}{{2\delta }}} \right),\;0 \le y \le \delta \) . The walls shear stress is given by:
A.	\({\tau _{wall}} = \;\frac{{\pi \mu {U_\infty }}}{{2\delta }}\)
B.	\({\tau _{wall}} = \;\frac{{3\pi \mu {U_\infty }}}{{\delta }}\)
C.	\({\tau _{wall}} = \;\frac{{2\pi \mu {U_\infty }}}{{\delta }}\)
D.	\({\tau _{wall}} = \;\frac{{\pi \mu {U_\infty }}}{{\delta }}\)
Answer» B. \({\tau _{wall}} = \;\frac{{3\pi \mu {U_\infty }}}{{\delta }}\)

Discussion

7.	An ideal fluid:
A.	viscous but incompressible
B.	has no viscosity and incompressible
C.	viscous at low temperature
D.	is viscous and compressible
Answer» C. viscous at low temperature

Discussion

8.	Mercury does NOT wet the glass. This is due to the property of the liquid known as
A.	Viscosity
B.	Surface tension
C.	Adhesion
D.	Cohesion
Answer» C. Adhesion

Discussion

9.	If angle of contact of a drop of liquid is acute, then
A.	Cohesion is equal to adhesion
B.	Cohesion is more than adhesion
C.	Adhesion is more than cohesion
D.	Both adhesion and cohesion have no connection with angle of contact
Answer» D. Both adhesion and cohesion have no connection with angle of contact

Discussion

10.	If the surface tension of the soap bubble is 0.035 N/m, then the work done in blowing the soap bubble of radius 5 cm in the air is.
A.	220 mJ
B.	2.2 mJ
C.	22 mJ
D.	0.22 mJ
Answer» C. 22 mJ

Discussion

11.	MKS unit of viscosity is -
A.	\(\dfrac{N - \sec}{m^2}\)
B.	\(\dfrac{kgf - \sec}{m^2}\)
C.	\(\dfrac{dyne - \sec}{cm^2}\)
D.	\(\dfrac{N }{m^2-\sec}\)
Answer» C. \(\dfrac{dyne - \sec}{cm^2}\)

Discussion

12.	According to the power-law model, \(\mu = m\;{\left\| {\frac{{du}}{{dy}}} \right\|^{n - 1}}\). What is the flow behavior index ‘n’ for pseudoplastic fluids?
A.	n = 0
B.	n = 1
C.	n < 1
D.	n > 1
Answer» D. n > 1

Discussion

13.	Dynamic viscosity of most of the gases with rise in temperature...
A.	Increases
B.	Decreases
C.	Remains unaffected
D.	Unpredictable
Answer» B. Decreases

Discussion

14.	An isentropic process is
A.	adiabatic and irreversible
B.	adiabatic and frictionless
C.	reversible and isothermal
D.	any adiabatic process
E.	any frictionless process
Answer» C. reversible and isothermal

Discussion

15.	______ fluid is incompressible.
A.	Newtonian
B.	Non-Newtonian
C.	Ideal
D.	Real
Answer» D. Real

Discussion

16.	In a capillary tube, the weight of the liquid raised is supported by:
A.	friction of tube
B.	vertical component of surface tension
C.	atmospheric pressure
D.	vapour pressure
Answer» C. atmospheric pressure

Discussion

17.	Consider two flat parallel plates placed in horizontal condition 1.2 cm apart and the space between them is filled with the oil of viscosity 15.0 poise. The upper plate is moved with a velocity of 3.25 m/s, then the shear stress in the oil is
A.	Between 100 - 150 N /m2
B.	Between 151 - 200 N/m2
C.	Between 201 - 350 N/m2
D.	Between 351 - 450 N/m2
Answer» E.

Discussion

18.	Dynamic viscosity of the gas
A.	Increases as temperature decreases
B.	Increases as temperature increases
C.	Is independent of temperature
D.	May increases or decreases with increases in temperature, depending on the nature of gas
Answer» C. Is independent of temperature

Discussion

19.	Dynamic viscosity of most liquids with rise in temperature
A.	Increases
B.	Decreases
C.	Remains unaffected
D.	Unpredictable
Answer» C. Remains unaffected

Discussion

20.	For a Newtonian fluid
A.	shear stress is proportional to shear strain
B.	rate of shear stress is proportional to shear strain
C.	shear stress is proportional to rate of shear strain
D.	rate of shear stress is proportional to rate of shear strain
Answer» D. rate of shear stress is proportional to rate of shear strain

Discussion

21.	For fluid the shear stress is directly proportional to:
A.	strain rate
B.	size
C.	strain
D.	shape
Answer» B. size

Discussion

22.	In C.G.S unit, dynamic viscosity is expressed as:
A.	Poise
B.	Pa-s
C.	Stoke
D.	None of the above
Answer» B. Pa-s

Discussion

23.	Hydrometer is an instrument for measuring
A.	relative humidity
B.	pressure of water
C.	volume of liquids
D.	specific gravity
Answer» E.

Discussion

24.	Group I contains the types of fluids while Group II contains the shear stress - rate of shear relationship of different types of fluids, as shown in the figure.Group IGroup IIP. Newtonian fluid1. Curve 1Q. Pseudo Plastic fluid2. Curve 2R. Plastic fluid3. Curve 3S. Dialatant fluid4. Curve 4 5. Curve 5 The correct match between Group I and Group II is
A.	P-2, Q-4, R-1, S-5
B.	P-2, Q-5, R-4, S-1
C.	P-2, Q-4, R-5, S-3
D.	P-2, Q-1, R-3, S-4
Answer» D. P-2, Q-1, R-3, S-4

Discussion

25.	Dimension of specific volume is:
A.	L3M-1T0
B.	L3M1T1
C.	L3M1T2
D.	L1M3T0
Answer» B. L3M1T1

Discussion

26.	Kinematic viscosity is the ratio of:
A.	Absolute viscosity to density of liquid
B.	Density of liquid to absolute viscosity
C.	Mass of liquid to absolute viscosity
D.	Absolute viscosity to mass of the liquid
Answer» B. Density of liquid to absolute viscosity

Discussion

27.	In SI system the unit of dynamic viscosity is
A.	N-s/m2
B.	N-m/s2
C.	Stoke
D.	Poise
Answer» B. N-m/s2

Discussion

28.	Oil spreads on the surface of water because _____
A.	oil is lighter than water
B.	oil is heavier than water
C.	oil has low vapour pressure
D.	of surface tension effect
Answer» E.

Discussion

29.	Capillary action is due to: _____.
A.	Adhesion
B.	Cohesion
C.	Adhesion and cohesion both
D.	Neither adhesion nor cohesion
Answer» D. Neither adhesion nor cohesion

Discussion

30.	An oil of specific gravity 0.9 has viscosity of 0.28 Stokes at 38°C. What will be its viscosity in Ns/m2 ?
A.	0.252
B.	0.0311
C.	0.0252
D.	0.0206
Answer» D. 0.0206

Discussion

31.	Cavitation parameter is defined by
A.	\(\frac{{{P_v} - P}}{{\frac{{p{V^2}}}{2}}}\)
B.	\(\frac{{{P_{atm}} - {P_v}}}{{\frac{{p{V^2}}}{2}}}\)
C.	\(\frac{{P - {P_{atm}}}}{{\frac{{\rho {V^2}}}{2}}}\)
D.	\(\frac{{P - {P_v}}}{{\frac{{\rho {V^2}}}{2}}}\)
Answer» E.

Discussion

32.	For Newtonian fluid behaviour, the shear stress exerted by the fluid is equal to the _______.
A.	Fluid viscosity divided by the velocity gradient parallel to the direction of shear
B.	Fluid viscosity divided by the velocity gradient perpendicular to the direction of shear
C.	A product of the fluid viscosity and the velocity gradient parallel to the direction of shear
D.	Product of the fluid viscosity and the velocity gradient perpendicular to the direction of shear
Answer» E.

Discussion

33.	For liquids, the values of dynamic viscosity (μ) and kinematic viscosity (ν) are
A.	Highly dependent of variation of pressure
B.	Practically independent of variation of pressure
C.	Practically independent of variation of temperature
D.	Increases with increase in temperature
Answer» C. Practically independent of variation of temperature

Discussion

34.	If 'd' is the diameter of a bubble and 's' represents the surface tension, what is the pressure inside the bubble?
A.	4s/d
B.	4d/s
C.	4s/3d
D.	8s/d
Answer» E.

Discussion

35.	A fluid in which shear is more than the yield and shear stress is proportional to the rate of shear strain, is:
A.	ideal plastic fluid
B.	real fluid
C.	ideal fluid
D.	Newtonian fluid
Answer» B. real fluid

Discussion

36.	A perfect fluid is
A.	compressible and gaseous
B.	a real fluid
C.	incompressible and frictionless
D.	one which obeys perfect gas laws
Answer» D. one which obeys perfect gas laws

Discussion

37.	A fluid in which shear stress is more than yield and shear stress is proportional to shear strain is known as ________
A.	Ideal fluid
B.	Newtonian
C.	Non-Newtonian
D.	Ideal plastic
Answer» E.

Discussion

38.	A reservoir of capacity 0.01 m3 is completely filled with a fluid of coefficient of compressibility 0.75 × 10-9 m2/N. The amount of fluid that will spill over (in m3), if pressure in the reservoir is reduced by 2 × 107 N/m2 is
A.	1 × 10-4
B.	1.5 × 10-4
C.	0.15 × 10-4
D.	None of the above
Answer» C. 0.15 × 10-4

Discussion

39.	A point through which the force of buoyancy is supposed to act is called:
A.	buoyancy
B.	centre of buoyancy
C.	metacentre
D.	metacentric height
E.	submerged height
Answer» C. metacentre

Discussion

40.	An oil has kinematic viscosity of 1.5 × 10-4 m2/s and specific gravity of 0.6, what is the dynamic viscosity in kg/ms units
A.	9 kg/ms
B.	0.09 kg/ms
C.	0.9 kg/ms
D.	0.009 kg/ms
Answer» C. 0.9 kg/ms

Discussion

41.	Newton's law of viscosity depends upon
A.	shear stress, pressure and velocity
B.	shear stress and strain in the fluid
C.	shear stress and rate of strain
D.	viscosity and shear stress
Answer» D. viscosity and shear stress

Discussion

42.	In order to prevent the capillary action from affecting the column of liquid in a piezometer the diameter of the glass tube should be
A.	less than 3 mm
B.	more than 3 mm but less than 5 mm
C.	equal to 5 mm
D.	greater than 6 mm
Answer» E.

Discussion

43.	If the pressure difference between the inside and outside of a soap bubble of 3 mm diameter is 16 N/m2, then surface tension will be
A.	0.12 N/m
B.	1.2 × 10-3 N/m
C.	1.2 N/m
D.	6.0 × 10-3 N/m
Answer» E.

Discussion

44.	A cubic wooden block of edge 100 mm and weight 1 kN is sliding down on an inclined plane of inclination 30° with the horizontal. A Newtonian fluid with the viscosity 0.2 Ns/m2 is layered on the inclined plane. If the thickness of the layer is 0.02 mm, then the terminal velocity of the block in m/s.
A.	0.25
B.	2.5
C.	5
D.	0.5
Answer» D. 0.5

Discussion

45.	Oil in a hydraulic cylinder is compressed from an initial volume of 2 m3 to 1.96 m3. If the pressure of oil in the cylinder changes from 40 MPa to 80 MPa during compression, the bulk modulus of elasticity of oil is
A.	1000 MPa
B.	2000 MPa
C.	4000 MPa
D.	8000 MPa
Answer» C. 4000 MPa

Discussion

46.	A Newtonian fluid fills the clearance between a shaft and a sleeve. When a force of 0.9 kN is applied to the shaft parallel to the sleeve, the shaft attains a speed of 1.25 cm/s. What will be the speed of the shaft if a force of 3 kN is applied?
A.	4.16 cm/s
B.	5.19 cm/s
C.	5.26 cm/s
D.	6.32 cm/s
Answer» B. 5.19 cm/s

Discussion

47.	In the case of capillarity, the rise or fall of head 'h' in a capillary tube of diameter 'd', liquid surface tension 'σ' and specific weight w is given by
A.	4σ/wd
B.	4dσ/w
C.	4wd/σ
D.	4d/σw
Answer» B. 4dσ/w

Discussion

48.	For the hydrostatic pressure measurement in fluids at rest
A.	The shear stress depends upon the coefficient of viscocity
B.	The shear stress is maximum on a plane inclined 45° to horizontal
C.	The shear stress is zero
D.	The shear stress is zero only on horizontal plane
Answer» D. The shear stress is zero only on horizontal plane

Discussion

49.	Pick the correct statement about viscosity.
A.	In general, it decreases with temperature for liquids because the internal force of attraction between two fluid layers gets decreased.
B.	In general, it decreases with temperature for gases because the internal force of attraction between two fluid layers gets decreased.
C.	In general, it increases with temperature for liquids because the internal force of attraction between two fluid layers gets increased.
D.	In general, it increases with temperature for gases because the internal force of attraction between two fluid layers gets increased.
Answer» B. In general, it decreases with temperature for gases because the internal force of attraction between two fluid layers gets decreased.

Discussion

50.	Find the change in height (h) in a circular tube (of radius R = 1 mm) filled with liquid (water) with surface tension T = 0.073 N / m. The contact angle of the water-air-glass interface is 0°.
A.	1.5 cm
B.	2.5 cm
C.	0.5 cm
D.	0.15 cm
Answer» B. 2.5 cm

Discussion

Explore topic-wise MCQs in Fluid Mechanics.

How does the viscosity of fluids vary with increase in temperature?

An increase in pressure of a liquid from 7.5 MPa to 15 MPa results into 0.2 percent decrease in its volume. The coefficient of compressibility of the liquid in m2/N is

A liquid compressed in cylinder has a volume of 0.04 m3 at 50 kg/cm2 and a volume of 0.039 m3 at 150 kg/cm2. The bulk modulus of liquid is

Newton’s law of viscosity states that:

A disc of radius R rotates at an angular velocity Ω inside a disc shaped container filled with oil of viscosity μ, as shown in figure. Assuming a linear velocity profile and neglecting shear stress on the outer disc edges, the formula for viscous torque on the disc is

A fluid near a solid wall has an approximated velocity profile given by \(u\left( y \right) = \;{U_\infty } \times \sin \left( {\frac{{\pi y}}{{2\delta }}} \right),\;0 \le y \le \delta \) . The walls shear stress is given by:

An ideal fluid:

Mercury does NOT wet the glass. This is due to the property of the liquid known as

If angle of contact of a drop of liquid is acute, then

If the surface tension of the soap bubble is 0.035 N/m, then the work done in blowing the soap bubble of radius 5 cm in the air is.

MKS unit of viscosity is -

According to the power-law model, \(\mu = m\;{\left| {\frac{{du}}{{dy}}} \right|^{n - 1}}\). What is the flow behavior index ‘n’ for pseudoplastic fluids?

Dynamic viscosity of most of the gases with rise in temperature...

An isentropic process is

______ fluid is incompressible.

In a capillary tube, the weight of the liquid raised is supported by:

Consider two flat parallel plates placed in horizontal condition 1.2 cm apart and the space between them is filled with the oil of viscosity 15.0 poise. The upper plate is moved with a velocity of 3.25 m/s, then the shear stress in the oil is

Dynamic viscosity of the gas

Dynamic viscosity of most liquids with rise in temperature

For a Newtonian fluid

For fluid the shear stress is directly proportional to:

In C.G.S unit, dynamic viscosity is expressed as:

Hydrometer is an instrument for measuring

Dimension of specific volume is:

Kinematic viscosity is the ratio of:

In SI system the unit of dynamic viscosity is

Oil spreads on the surface of water because _____

Capillary action is due to: _____.

An oil of specific gravity 0.9 has viscosity of 0.28 Stokes at 38°C. What will be its viscosity in Ns/m2 ?

Cavitation parameter is defined by

For Newtonian fluid behaviour, the shear stress exerted by the fluid is equal to the _______.

For liquids, the values of dynamic viscosity (μ) and kinematic viscosity (ν) are

If 'd' is the diameter of a bubble and 's' represents the surface tension, what is the pressure inside the bubble?

A fluid in which shear is more than the yield and shear stress is proportional to the rate of shear strain, is:

A perfect fluid is

A fluid in which shear stress is more than yield and shear stress is proportional to shear strain is known as ________

A reservoir of capacity 0.01 m3 is completely filled with a fluid of coefficient of compressibility 0.75 × 10-9 m2/N. The amount of fluid that will spill over (in m3), if pressure in the reservoir is reduced by 2 × 107 N/m2 is

A point through which the force of buoyancy is supposed to act is called:

An oil has kinematic viscosity of 1.5 × 10-4 m2/s and specific gravity of 0.6, what is the dynamic viscosity in kg/ms units

Newton's law of viscosity depends upon

In order to prevent the capillary action from affecting the column of liquid in a piezometer the diameter of the glass tube should be

If the pressure difference between the inside and outside of a soap bubble of 3 mm diameter is 16 N/m2, then surface tension will be

Oil in a hydraulic cylinder is compressed from an initial volume of 2 m3 to 1.96 m3. If the pressure of oil in the cylinder changes from 40 MPa to 80 MPa during compression, the bulk modulus of elasticity of oil is

A Newtonian fluid fills the clearance between a shaft and a sleeve. When a force of 0.9 kN is applied to the shaft parallel to the sleeve, the shaft attains a speed of 1.25 cm/s. What will be the speed of the shaft if a force of 3 kN is applied?

In the case of capillarity, the rise or fall of head 'h' in a capillary tube of diameter 'd', liquid surface tension 'σ' and specific weight w is given by

For the hydrostatic pressure measurement in fluids at rest

Pick the correct statement about viscosity.

Find the change in height (h) in a circular tube (of radius R = 1 mm) filled with liquid (water) with surface tension T = 0.073 N / m. The contact angle of the water-air-glass interface is 0°.