For the Stoke's law to be valid in the case of a falling sphere in a fluid, the
(A) Reynolds number (based on sphere diameter) should be < 1 (B) Flow around the sphere should be in turbulent region
(C) Sphere must be metallic
(D) Fluid density should be constant

1 Answer

Answer :

(C) Sphere must be metallic

Related questions

Description : The Sieder-Tate correlation for heat transfer in turbulent flow in pipe gives Nu α Re 0.8 , where, Nu is the Nusselt number and Re is the Reynolds number for the flow. Assuming that this relation is valid, the heat transfer co-efficient ... pipe diameter (D) as (A) D-1.8 (B) D-0.2 (C) D0.2 (D) D1.8

Last Answer : (B) D-0.2

Description : . In case of turbulent flow of fluid through a circular pipe, the (A) Mean flow velocity is about 0.5 times the maximum velocity (B) Velocity profile becomes flatter and flatter with ... , shear stresses, random orientation of fluid particles and slope of velocity profile at the wall are more

Last Answer : (D) Skin friction drag, shear stresses, random orientation of fluid particles and slope of velocity profile at the wall are more

Description : Stoke's law is valid, when the particle Reynolds number is (A) < 1 (B) > 1 (C) < 5 (D) None of these

Last Answer : (A) < 1

Description : Navier-Stokes equation is useful in the analysis of __________ fluid flow problems. (A) Non-viscous (B) Viscous (C) Turbulent (D) Rotational

Last Answer : (B) Viscous

Description : Pick out the wrong statement pertaining to fluid flow. (A) The ratio of average velocity to the maximum velocity for turbulent flow of Newtonian fluid in circular pipes is 0.5 (B) The Newtonian ... at the centre of the pipe (C) Navier-Stokes equation is applicable to the analysis of viscous flows

Last Answer : (A) The ratio of average velocity to the maximum velocity for turbulent flow of Newtonian fluid in circular pipes is 0.5

Description : Stoke's equation is valid in the Reynolds number range (A) 0.01 to 0.1 (B) 0.1 to 2 (C) 2 to 10 (D) 10 to 100

Last Answer : (A) 0.01 to 0.1

Description : Isothermal turbulent flow of a fluid results in decrease of its pressure, which depends on the (A) Wall roughness (B) Reynolds number (C) Both (A) & (B) (D) Neither (A) nor (B)

Last Answer : (C) Both (A) & (B)

Description : Which of the fluid forces are not considered in the Reynold's equation of flow? (A) Viscous forces (B) Turbulent forces (C) Pressure forces (D) Compressibility forces

Last Answer : (D) Compressibility forces

Description : Transition from laminar flow to turbulent flow in fluid flow through a pipe does not depend upon the (A) Length of the pipe (B) Diameter of the pipe (C) Density of the fluid (D) Velocity of the fluid

Last Answer : (A) Length of the pipe

Description : The terminal velocity of a sphere setting in a viscous fluid varies as : (a) The Reynolds number (b) The square of its diameter (c) Directly proportional to the viscosity of the fluid (d) Its diameter

Last Answer : (b) The square of its diameter

Description : In a fully turbulent flow (Re > 10 5 ) in a pipe of diameter 'd', for a constant pressure gradient, the dependence of volumetric flow rate of an incompressible fluid is (A) d (B) d 2 (C) d 2.5 (D) d

Last Answer : (C) d 2.5

Description : Convective heat transfer co-efficient in case of fluid flowing in tubes is not affected by the tube length/diameter ratio, if the flow is in the __________ zone. (A) Laminar (B) Transition (C) Both 'a' & 'b' (D) Highly turbulent

Last Answer : (D) Highly turbulent

Description : Pick out the wrong statement: (A) Greater is the kinematic viscosity of the liquid, greater is the thickness of the boundary layer (B) Blowers develop a maximum pressure of 2 atmospheres ( ... factor in case of turbulent flow of liquids in pipe depends upon relative roughness & Reynolds number

Last Answer : (C) Friction losses in pipe fittings are generally expressed in terms of velocity heads

Description : The terminal velocity of a solid spherical particle falling through a stationary fluid mass in the Stoke's law range is proportional to the (A) Inverse of fluid viscosity (B) Square of particle size (C) Difference in the densities of the particle & fluid (D) All (A), (B) and (C)

Last Answer : (D) All (A), (B) and (C)

Description : Pick out the wrong statement. (A) A fluid mass is free from shearing forces, when it is made to rotate with a uniform velocit (B) Newton's law of viscosity is not applicable to the ... types of bearings (D) Rise of water in capillary tubes reduces with the increasing diameter of capillary tubes

Last Answer : (B) Newton's law of viscosity is not applicable to the turbulent flow of fluid with linear velocity distribution

Description : _________ fluid force is not considered in the Navier-Stokes equation. (A) Turbulent (B) Viscous (C) Gravity (D) Pressure

Last Answer : (A) Turbulent

Description : Creeping flow around a sphere is defined, when particle Reynolds number is (A) < 2100 (B) < 0.1 (C) > 2.5 (D) < 500

Last Answer : (B) < 0.1

Description : The fluid forces considered in the Navier Stokes equation are (A) Gravity, pressure and viscous (B) Gravity, pressure and turbulent (C) Pressure, viscous and turbulent (D) Gravity, viscous and turbulent

Last Answer : Answer: Option A

Description : Two fluids are flowing through two similar pipes of the same diameter. The Reynold's number is same. For the same flow rate if the viscosity of a fluid is reduced to half the value of the ... (A) Increase (B) Decrease (C) Remain unchanged (D) Data insufficient to predict relative pressure drop

Last Answer : (B) Decrease

Description : For a sphere falling in the constant drag co-efficient regime, its terminal velocity depends on its diameter (D) as (A) d (B) √d (C) d 2 (D) 1/d

Last Answer : (C) d

Description : A fluid is flowing inside the inner tube of a double pipe heat exchanger with diameter 'd'. For a fixed mass flow rate, the tube side heat transfer co￾efficient for turbulent flow conditions is proportional to (A) d 0.8 (B) d -0.2 (C) d -1 (D) d -1.8

Last Answer : (B) d -0.2

Description : Transition length for a turbulent fluid entering into a pipe is around __________ times the pipe diameter. (A) 5 (B) 50 (C) 500 (D) 5000

Last Answer : (B) 50

Description : Critical value of the __________ number governs the transition from laminar to turbulent flow in free convection heat transfer. (A) Grashoff (B) Reynolds (C) Both 'a' & 'b' (D) Prandtl & Grashoff

Last Answer : (D) Prandtl & Grashoff

Description : The friction factor for turbulent flow in a hydraulically smooth pipe (A) Depends only on Reynolds number (B) Does not depend on Reynolds number (C) Depends on the roughness (D) None of these

Last Answer : (A) Depends only on Reynolds number

Description : When the pipe Reynold's number is 6000, the flow is generally (A) Viscous (B) Laminar (C) Turbulent (D) Transition

Last Answer : (C) Turbulent

Description : In turbulent flow, a rough pipe has the same friction factor as a smooth pipe (A) In the zone of complete turbulence (B) When the roughness projections are much smaller than the thickness of ... ) Everywhere in the transition zone (D) When the friction factor is independent of the Reynold's number

Last Answer : (B) When the roughness projections are much smaller than the thickness of the laminar film

Description : Nusselt number is related to the Reynolds number (Re) in turbulent & laminar flow respectively as (A) Re0.5, Re0.8 (B) Re0.8, Re-0.5 (C) Re0.8, Re0.5 (D) Re-0.8, Re0.5

Last Answer : (C) Re0.8, Re0.5

Description : For laminar flow of a fluid through a packed bed of spheres of diameter d, the pressure drop per unit length of bed depends upon the sphere diameter as (A) d (B) d 2 (C) d 4 (D) d

Last Answer : (D) d

Description : As the velocity V and thus the Reynolds number of a flow past a sphere increases from very low value, the drag force for Re

Last Answer : (A) Increases linearly with V

Description : For pipes, turbulent flow occurs when Reynolds number is (A) Less than 2000 (B) Between 2000 and 4000 (C) More than 4000 (D) Less than 4000

Last Answer : Answer: Option C

Description : Define. i) Streamline flow ii) Turbulent flow Give significance of Reynold’s number.

Last Answer : i) Streamline flow The flow of liquid in which every particle of liquid moves in the same direction of flow of liquid is called streamline flow. ii) Turbulent flow The flow of liquid in which every ... to 3000 liquid flow is unstable. (3)When R is greater than 3000 liquid flow is turbulent. 

Description : In case of turbulent flow of a Newtonian fluid in a straight pipe, the maximum velocity is equal to (where, Vavg = average fluid velocity) (A) Vavg (B) 1.2 Vavg (C) 1.5 Vavg (D) 1.8 Vavg

Last Answer : (B) 1.2 Vavg

Description : Pick out the wrong statement. (A) Surface tension of a liquid is because of the difference in magnitude of adhesive & cohesive forces (B) A hydrometer used for the determination of ... Turbulent fluid flow is characterised by the rapid fluctuation of instantaneous pressure & velocity at a poin

Last Answer : (C) In case of unsteady fluid flow, the velocity at any given point does not change with time

Description : Stoke's law is valid, when NRe, p is less than (A) 2 (B) 100 (C) 2100 (D) 700

Last Answer : (A) 2

Description : Pick out the correct statement. (A) A forced vortex occurs when fluid rotates as a solid about an axis (B) In laminar flow, Newton's law of viscosity does not apply (C) A free vortex occurs, when fluid rotates as a solid (D) In turbulent flow, there are neither cross-currents nor eddies

Last Answer : (A) A forced vortex occurs when fluid rotates as a solid about an axis

Description : Pick out the wrong statement. (A) The form drag is dependent upon the occurrence of a wake (B) The shear stress at any given cross-section of a pipe for steady flow (either laminar or turbulent ... of viscosity (D) Existence of the boundary layer in fluid flow is because of viscosity of the fluid

Last Answer : (C) An ideal fluid is the one, which has negligible surface tension and obeys the Newton's law of viscosity

Description : The fluid velocity varies as the cube of the cylindrical pipe diameter in case of steady state laminar flow at constant pressure drop for __________ fluid. (A) Newtonian (B) Pseudo-plastic (C) Dilatent (D) Bingham plastic

Last Answer : (B) Pseudo-plastic

Description : The fluid velocity varies as the square of the cylindrical pipe diameter, in case of steady state laminar flow at constant pressure drop, for __________ fluid. (A) Newtonian (B) Dilatant (C) Pseudo-plastic (D) Non-Newtonian

Last Answer : (A) Newtonian

Description : The fluid velocity varies as the square root of the cylindrical pipe diameter in case of steady state laminar flow at constant pressure drop of __________ fluid. (A) Dilatent (B) Pseudo-plastic (C) Bingham plastic (D) Newtonian

Last Answer : (A) Dilatent

Description : Dittus-Boelter equation used for the determination of heat transfer co￾efficient is valid (A) For fluids in laminar flow (B) For fluids in turbulent flow (C) When Grashoff number is very important (D) For liquid metals

Last Answer : (B) For fluids in turbulent flow

Description : Heat transfer co-efficient equation for forced convection, Nu = 0.023 Re 0.8 . Pr n , is not valid, if the value of (A) n = 0.4 is used for heating (B) n = 0.3 is used for cooling (C) Reynolds number for the flow involved is > 10000 (D) Reynolds number for the flow involved is < 2100

Last Answer : (D) Reynolds number for the flow involved is < 2100

Description : Stoke's law is valid only if the size of particle is (A) Less than 0.0002 mm (B) Greater than 0.2 mm (C) Between 0.2 mm and 0.0002 mm (D) All of the above

Last Answer : Answer: Option C

Description : At low Reynold's number, the power (P) required for agitating a fluid in a stirred tank becomes independent of inertial forces. In this limit, indicate which of the following relations is satisfied: Po = ρ/ρN3 D5 : Power number Re = ρ N D2 ... Re -1.0 (B) Po ∝ Re 0.0 (C) Po ∝ Re 0.5 (D) Po ∝ Re 1.0

Last Answer : (B) Po ∝ Re 0.0 (C) Po ∝ Re 0.5

Description : Reynolds number of a fluid flowing in a circular pipe is 10,000. What will be the Reynolds number when the fluid velocity is decreased by 30% & the pipe diameter is increased by 30%? (A) 9,100 (B) 13,000 (C) 7,000 (D) 2,550

Last Answer : (A) 9,100

Description : f = 16/NRe , is valid for (A) Turbulent flow (B) Laminar flow through an open channel (C) Steady flow (D) None of these

Last Answer : (D) None of these

Description : A metallic hallow sphere of 8cm diameter is charged with 4 × 10−8c. The potential on its surface will be: (a) 90 volts (b) 9 volts (c) 9000 volts (d) 900 volts

Last Answer : c) 9000 volts

Description : In Newton's law range, the terminal velocity of a solid spherical particle falling through a stationary fluid mass varies as the __________ of its diameter. (A) Inverse (B) Square root (C) Second power (D) First power

Last Answer : (B) Square root

Description : The ratio of the wall drag to the form drag in the Stoke's law range (for motion of spherical particles in a stationary fluid) is (A) 0.5 (B) 1 (C) 2 (D) 0.33

Last Answer : (C) 2

Description : The terminal velocity of a particle moving through a fluid varies as dp n . The value of n is equal to __________ in Stoke's law regime. (A) 1 (B) 0.5 (C) 2 (D) 1.5

Last Answer : (C) 2