Starting friction is low in case of the __________ lubrication. (A) Boundary (B) Hydrodynamic (C) Hydrostatic (D) Mixed/semi-fluid

Starting friction is low in case of the __________ lubrication. (A) Boundary
(B) Hydrodynamic
(C) Hydrostatic
(D) Mixed/semi-fluid
by

1 Answer

Answer :

(C) Hydrostatic
by

Related questions

Assertion (A): Hydrostatic lubrication is more advantageous when compared to hydrodynamic lubrication during starting and stopping the journal in its bearing. Reason (R): In hydrodynamic lubrication, the fluid film pressure is generated by the rotation of the journal. [IES-1998] (a) Both A and R are individually true and R is the correct explanation of A (b) Both A and R are individually true but R is not the correct explanation of A (c) A is true but R is false (d) A is false but R is true

Description : Assertion (A): Hydrostatic lubrication is more advantageous when compared to hydrodynamic lubrication during starting and stopping the journal in its bearing. Reason (R): In hydrodynamic lubrication, the fluid film pressure is ... (c) A is true but R is false (d) A is false but R is true

Last Answer : (b) Both A and R are individually true but R is not the correct explanation of A

Assertion (A): Oil as a cutting fluid result in a lower coefficient of friction. Reason (R): Oil forms a thin liquid film between the tool face and chip, and it provides 'hydrodynamic lubrication'. [IES- 2000] (a) Both A and R are individually true and R is the correct explanation of A (b) Both A and R are individually true but R is not the correct explanation of A (c) A is true but R is false (d) A is false but R is true

Description : Assertion (A): Oil as a cutting fluid result in a lower coefficient of friction. Reason (R): Oil forms a thin liquid film between the tool face and chip, and it provides 'hydrodynamic lubrication'. [IES- 2000] (a ... explanation of A (c) A is true but R is false (d) A is false but R is true

Last Answer : (c) A is true but R is false

Hydrostatic and hydrodynamic lubrication are the same thing. a) True b) False

Description : Hydrostatic and hydrodynamic lubrication are the same thing. a) True b) False

Last Answer : b) False

How does the hydrostatic lubrication differ from hydrodynamic type?

Description : How does the hydrostatic lubrication differ from hydrodynamic type?

Last Answer : In hydrostatic lubrication which is used in slow speed turbines the lubricating oil is pressurised externally where as in hydrodynamic system it forms oil film by its speed which pushes the lubrication oil to form film.

Boundary lubricated bearing is (A) Thick film bearing (B) Thin film bearing (C) Hydrodynamic bearing (D) Hydrostatic bearing

Description : Boundary lubricated bearing is (A) Thick film bearing (B) Thin film bearing (C) Hydrodynamic bearing (D) Hydrostatic bearing

Last Answer : (B) Thin film bearing

At what value of Prandtl number, the hydrodynamic and thermal boundary layers of a fluid flowing over a heated plate will be identical? (A) 1 (B) < 1 (C) > 1 (D) None of these

Description : At what value of Prandtl number, the hydrodynamic and thermal boundary layers of a fluid flowing over a heated plate will be identical? (A) 1 (B) < 1 (C) > 1 (D) None of these

Last Answer : (A) 1

Match List I with List II and select the : [IES-2002] List I (Bearings) List II (Load type) A. Hydrodynamic Journal bearing 1. High radial and thrust load combined B. Rectangular Hydrostatic bearing 2. Radial load only C. Taper Roller bearing 3. Thrust load only D. Angular contact ball bearing 4. Medium to low radial and thrust combined A B C D A B C D (a) 2 3 1 4 (b) 4 1 3 2 (c) 2 1 3 4 (d) 4 3 1 2

Description : Match List I with List II and select the : [IES-2002] List I (Bearings) List II (Load type) A. Hydrodynamic Journal bearing 1. High radial and thrust load combined B. Rectangular Hydrostatic bearing 2. Radial load only C. Taper Roller ... (a) 2 3 1 4 (b) 4 1 3 2 (c) 2 1 3 4 (d) 4 3 1 2

Last Answer : (a) 2 3 1 4

The ratio of hydrodynamic boundary layer to thermal boundary layer thickness in case of liquid metals is (A) < 1 (B) 1 (C) > 1 (D) 2

Description : The ratio of hydrodynamic boundary layer to thermal boundary layer thickness in case of liquid metals is (A) < 1 (B) 1 (C) > 1 (D) 2

Last Answer : (A) < 1

Which one of the following pair is correctly matched? [IES-2000] (a) Beauchamp tower ........................First experiments on journal bearings (b) Osborne Reynolds ........................Antifriction bearings (c) Somerfield number........................Pivot and Collar bearings (d) Ball bearings...............................Hydrodynamic lubrication

Description : Which one of the following pair is correctly matched? [IES-2000] (a) Beauchamp tower ........................First experiments on journal bearings (b) Osborne Reynolds ........................ ... .Pivot and Collar bearings (d) Ball bearings...............................Hydrodynamic lubrication

Last Answer : (a) Beauchamp tower ........................First experiments on journal bearings

A journal bearing with hydrodynamic lubrication is running steadily with a certain amount of minimum film thickness. When the load and speed are doubled, how does the minimum film thickness vary? [IES-2008] (a) Remains unchanged (b) Gets doubled (c) Gets reduced to one-fourth of original value (d) Gets reduced to half of original value

Description : A journal bearing with hydrodynamic lubrication is running steadily with a certain amount of minimum film thickness. When the load and speed are doubled, how does the minimum film thickness vary? [IES-2008 ... Gets reduced to one-fourth of original value (d) Gets reduced to half of original value

Last Answer : (a) Remains unchanged

For elasto-hydrodynamic lubrication (A) There should be relative motion between the surfaces of the journal and the bearing and wedge shaped clearance space (B) There should be external source like pump to supply lubricant under pressure (C) There should be elastic deformation of the parts in contact (D) There should be metal to metal contact

Description : For elasto-hydrodynamic lubrication (A) There should be relative motion between the surfaces of the journal and the bearing and wedge shaped clearance space (B) There should be external source like ... be elastic deformation of the parts in contact (D) There should be metal to metal contact

Last Answer : (C) There should be elastic deformation of the parts in contact

For hydrodynamic lubrication (A) There should be relative motion between the surfaces of the journal and the bearing and wedge shaped clearance space (B) There should be external source like pump to supply lubricant under pressure (C) There should be elastic deformation of the parts in contact (D) There should be metal to metal contact

Description : For hydrodynamic lubrication (A) There should be relative motion between the surfaces of the journal and the bearing and wedge shaped clearance space (B) There should be external source like pump to ... be elastic deformation of the parts in contact (D) There should be metal to metal contact

Last Answer : (A) There should be relative motion between the surfaces of the journal and the bearing and wedge shaped clearance space

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

Description : 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

Last Answer : b) Increase with increase in speed

A journal bearing is a ______ contact bearing working on the hydrodynamic lubrication and which supports load in____ direction. a) Sliding, Axial b) Rolling, Radial c) Sliding, Radial d) Rolling, Axial

Description : A journal bearing is a ______ contact bearing working on the hydrodynamic lubrication and which supports load in____ direction. a) Sliding, Axial b) Rolling, Radial c) Sliding, Radial d) Rolling, Axial

Last Answer : c) Sliding, Radial

What is meant by hydrodynamic film lubrication?

Description : What is meant by hydrodynamic film lubrication?

Last Answer : In high-speed turbines the lubricating oil will be at the sides and there is metal to metal contact when turbine at rest. When the turbine speeds up there is pressure pushing the oil through the ... the oil film breaks the barrier and it takes the load on itself. This is hydrodynamic lubrication. 

For hydrostatic lubrication (A) There should be relative motion between the surfaces of the journal and the bearing and wedge shaped clearance space (B) There should be external source like pump to supply lubricant under pressure (C) There should be elastic deformation of the parts in contact (D) There should be metal to metal contact

Description : For hydrostatic lubrication (A) There should be relative motion between the surfaces of the journal and the bearing and wedge shaped clearance space (B) There should be external source like pump to ... be elastic deformation of the parts in contact (D) There should be metal to metal contact

Last Answer : (B) There should be external source like pump to supply lubricant under pressure

In hydrostatic bearings (A) The Oil film pressure is generated only by the rotation of the journal (B) The oil film is maintained by supplying oil under pressure (C) Do not require external supply of lubricant (D) Grease is used for lubrication

Description : In hydrostatic bearings (A) The Oil film pressure is generated only by the rotation of the journal (B) The oil film is maintained by supplying oil under pressure (C) Do not require external supply of lubricant (D) Grease is used for lubrication

Last Answer : (B) The oil film is maintained by supplying oil under pressure

The most suitable bearing for carrying very heavy loads with slow speed is (a) Hydrodynamic bearing (b) ball bearing [IAS 1994] (c) Roller bearing (d) hydrostatic bearing

Description : The most suitable bearing for carrying very heavy loads with slow speed is (a) Hydrodynamic bearing (b) ball bearing [IAS 1994] (c) Roller bearing (d) hydrostatic bearing

Last Answer : (d) hydrostatic bearing

If we exclude the cost factor, which bearing is preferred? a) Hydrostatic b) Hydrodynamic c) Both are equally preferred d) Cannot be determined

Description : If we exclude the cost factor, which bearing is preferred? a) Hydrostatic b) Hydrodynamic c) Both are equally preferred d) Cannot be determined

Last Answer : a) Hydrostatic

The pressure that builds up in pore water due to load increment on the soil, is termed (A) Excess pore pressure (B) Excess hydrostatic pressure (C) Hydrodynamic pressure (D) All the above

Description : The pressure that builds up in pore water due to load increment on the soil, is termed (A) Excess pore pressure (B) Excess hydrostatic pressure (C) Hydrodynamic pressure (D) All the above

Last Answer : Answer: Option D

Satisfactory hydrodynamic film in a journal bearing is formed when (a) Journal speed is low; unit pressure on the bearing is high and viscosity of lubricant used is low [IES-2006] (b) Journal speed is low; unit pressure on the bearing is low and viscosity of lubricant used is low (c) Journal speed is high; unit pressure on the bearing is high and viscosity of lubricant used is high (d) Appropriate combination of journal speed, unit pressure on bearing and lubricant viscosity exists resulting in low coefficient of friction

Description : Satisfactory hydrodynamic film in a journal bearing is formed when (a) Journal speed is low; unit pressure on the bearing is high and viscosity of lubricant used is low [IES-2006] ... journal speed, unit pressure on bearing and lubricant viscosity exists resulting in low coefficient of friction

Last Answer : (c) Journal speed is high; unit pressure on the bearing is high and viscosity of lubricant used is high

Pick out the wrong statement. (A) In the McCabe-Thiele diagram for binary distillation, vertical feed line represents saturated liquid feed and horizontal feed line represents saturated vapour feed (B) In small columns, local efficiency is larger than Murphree efficiency; in large columns local efficiency is smaller than Murphree efficiency (C) For Laminar flow over a plate of length L, the local mass transfer co￾efficient at a distance L from the leading edge is 1.5 × 10 -2m/s. Then the average mass transfer co-efficient for the plate is 2 × 10 -2m/s (D) The concentration and hydrodynamic boundary layers over a flat plate are of equal thickness, if Schmidt number is equal to unity

Description : Pick out the wrong statement. (A) In the McCabe-Thiele diagram for binary distillation, vertical feed line represents saturated liquid feed and horizontal feed line represents saturated vapour feed (B) In ... layers over a flat plate are of equal thickness, if Schmidt number is equal to unity

Last Answer : (C) For Laminar flow over a plate of length L, the local mass transfer co￾efficient at a distance L from the leading edge is 1.5 × 10 -2m/s. Then the average mass transfer co-efficient for the plate is 2 × 10 -2m/s

Thickness of thermal boundary layer is more compared to that of hydrodynamic boundary layer, when the value of Prandtl number is (A) 1 (B) < 1 (C) > 1 (D) > 5

Description : Thickness of thermal boundary layer is more compared to that of hydrodynamic boundary layer, when the value of Prandtl number is (A) 1 (B) < 1 (C) > 1 (D) > 5

Last Answer : (B) < 1

. If Prandtl number is greater than the Schmidt number, then the (A) Thermal boundary layer lies inside the concentration boundary layer (B) Concentration boundary layer lies inside the thermal boundary layer (C) Thermal & concentration boundary layers are of equal thickness (D) Hydrodynamic (i.e., momentum) boundary layer is thicker than the other two

Description : . If Prandtl number is greater than the Schmidt number, then the (A) Thermal boundary layer lies inside the concentration boundary layer (B) Concentration boundary layer lies inside the thermal boundary ... (D) Hydrodynamic (i.e., momentum) boundary layer is thicker than the other two

Last Answer : (A) Thermal boundary layer lies inside the concentration boundary layer

The thermal boundary layer at NPr > 1 (A) Is thicker than hydrodynamic boundary layer (B) Is thinner than hydrodynamic boundary layer (C) And the hydrodynamic boundary layers are identical (D) Disappears

Description : The thermal boundary layer at NPr > 1 (A) Is thicker than hydrodynamic boundary layer (B) Is thinner than hydrodynamic boundary layer (C) And the hydrodynamic boundary layers are identical (D) Disappears

Last Answer : (B) Is thinner than hydrodynamic boundary layer

For flow over a flat plate, the ratio of thermal boundary layer thickness, 'xt' and hydrodynamic boundary layer thickness 'x' is equal to (where, NPr = Prandtl number) (A) NPr (B) NPr 1/3 (C) NPr -1 (D) NPr -1/3

Description : For flow over a flat plate, the ratio of thermal boundary layer thickness, 'xt' and hydrodynamic boundary layer thickness 'x' is equal to (where, NPr = Prandtl number) (A) NPr (B) NPr 1/3 (C) NPr -1 (D) NPr -1/3

Last Answer : (B) NPr 1/3

The hydrodynamic and thermal boundary layers will merge, when (A) Prandtl number is one (B) Schmidt number tends to infinity (C) Nusselt number tends to infinity (D) Archimedes number is greater than 10000

Description : The hydrodynamic and thermal boundary layers will merge, when (A) Prandtl number is one (B) Schmidt number tends to infinity (C) Nusselt number tends to infinity (D) Archimedes number is greater than 10000

Last Answer : (A) Prandtl number is one

The major reason of hydrodynamic noise (i.e., noise resulting from liquid flow) is (A) Pipe vibrations (B) Cavitation (C) Boundary layer separation (D) Fluctuation in liquid flow

Description : The major reason of hydrodynamic noise (i.e., noise resulting from liquid flow) is (A) Pipe vibrations (B) Cavitation (C) Boundary layer separation (D) Fluctuation in liquid flow

Last Answer : (B) Cavitation

If fluid film pressure is high and surface rigidity is low than mode of lubrication is called as elastohydrodynamic lubrication. a) True b) False

Description : If fluid film pressure is high and surface rigidity is low than mode of lubrication is called as elastohydrodynamic lubrication. a) True b) False

Last Answer : a) True

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 (C) Friction losses in pipe fittings are generally expressed in terms of velocity heads (D) Fanning friction factor in case of turbulent flow of liquids in pipe depends upon relative roughness & Reynolds number

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

Explain boundary lubrication with diagram.

Description : Explain boundary lubrication with diagram.

Last Answer : Boundary lubrication: This type of lubrication is done when a continuous fluid film of lubricant cannot persist & direct metal to metal contact is possible due to certain reasons. This happens when i) a ... which is responsible for this kind of adsorption is Oiliness.   Diagram 

How the thickness of thermal boundary layer and thickness of hydrodynamic boundary layer related ?

Description : How the thickness of thermal boundary layer and thickness of hydrodynamic boundary layer related ?

Last Answer : Ratio of their thickness = (Prandtl number)-1/3.

02. The separation of flow occurs when the hydrodynamic boundary layer thickness is reduced to zero. A) AgreeB) Disagree

Description : 02. The separation of flow occurs when the hydrodynamic boundary layer thickness is reduced to zero. A) Agree B) Disagree

Last Answer : A

The purpose of lubrication in an antifriction bearing is (a) to reduce the friction between balls and races (b) dissipation of frictional heat prevention of corrosion (c) protection of the bearing from dirt and other foreign particles (d) all of the mentioned

Description : The purpose of lubrication in an antifriction bearing is (a) to reduce the friction between balls and races (b) dissipation of frictional heat prevention of corrosion (c) protection of the bearing from dirt and other foreign particles (d) all of the mentioned

Last Answer : (d) all of the mentioned

Increase in values of which of the following results in an increase of the coefficient of friction in a hydrodynamic bearing? [IES 2007] 1. Viscosity of the oil. 2. Clearance between shaft and bearing. 3. Shaft speed. Select the using the code given below: (a) 1 and 2 only (b) 1 and 3 only (c) 2 and 3 only (d) 1, 2 and 3

Description : Increase in values of which of the following results in an increase of the coefficient of friction in a hydrodynamic bearing? [IES 2007] 1. Viscosity of the oil. 2. Clearance between shaft and bearing. 3. Shaft speed. Select the ... 1 and 2 only (b) 1 and 3 only (c) 2 and 3 only (d) 1, 2 and 3

Last Answer : (b) 1 and 3 only

For winds that last six hours or more, such as a midlatitude storm, the air movement is modified by which causes the air to be deflected to . (a) Hydrostatic Force; the right in the Northern Hemisphere (b) Coriolis Force; the right in the Northern Hemisphere (c) Friction; the left in the Northern Hemisphere (d) Coriolis Force; the left in the Northern Hemisphere

Description : For winds that last six hours or more, such as a midlatitude storm, the air movement is modified by which causes the air to be deflected to . (a) Hydrostatic Force; the right in the ... c) Friction; the left in the Northern Hemisphere (d) Coriolis Force; the left in the Northern Hemisphere

Last Answer : (b) Coriolis Force; the right in the Northern Hemisphere

Pick out the wrong statement. (A) A fluid mass is free from shearing forces, when it is made to rotate with a uniform velocity(B) Newton's law of viscosity is not applicable to the turbulent flow of fluidwith linear velocity distribution(C) Laminar flow of viscous liquids is involved in the lubrication of varioustypes of bearings(D) Rise of water in capillary tubes reduces with the increasing diameter ofcapillary tubes

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

With the increase in depth, the hydrostatic pressure in an un-accelerated incompressible fluid (in a constant gravitational field) (A) Decreases (B) Increases linearly (C) Increases exponentially (D) Remain constant

Description : With the increase in depth, the hydrostatic pressure in an un-accelerated incompressible fluid (in a constant gravitational field) (A) Decreases (B) Increases linearly (C) Increases exponentially (D) Remain constant

Last Answer : (B) Increases linearly

Which of the following forces does not act on a fluid at rest? (A) Viscous force (B) Gravity force (C) Hydrostatic force (D) Surface tension force

Description : Which of the following forces does not act on a fluid at rest? (A) Viscous force (B) Gravity force (C) Hydrostatic force (D) Surface tension force

Last Answer : (A) Viscous force

In fluid flow, the boundary layer separation cannot occur (A) In case of boundaries experiencing form drag (B) At points of abrupt changes in the flow directions (C) In laminar flow (D) None of these

Description : In fluid flow, the boundary layer separation cannot occur (A) In case of boundaries experiencing form drag (B) At points of abrupt changes in the flow directions (C) In laminar flow (D) None of theseIn ... B) At points of abrupt changes in the flow directions (C) In laminar flow (D) None of these

Last Answer : (D) None of these

. 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 increasing Reynolds number (C) Point of maximum instability exists at a distance of 2r/3 from the pipe wall (r = pipe radius) (D) Skin friction drag, shear stresses, random orientation of fluid particles and slope of velocity profile at the wall are more

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

During its operation, loud buzzing and resultant welding of contacts of a magnetic relay may be caused by __________. A. overheating of the contactor coil B. low voltage on the operating coil C. low insulation resistance to ground D. lubrication of the contact bearing points

Description : During its operation, loud buzzing and resultant welding of contacts of a magnetic relay may be caused by __________. A. overheating of the contactor coil B. low voltage on the operating coil C. low insulation resistance to ground D. lubrication of the contact bearing points

Last Answer : Answer: B

The effect of solid boundary on the fluid flow is confined to the boundary layer, except for fluids (A) Having high viscosities (B) Moving at low velocities (C) Both (A) & (B) (D) Neither (A) nor (B)

Description : The effect of solid boundary on the fluid flow is confined to the boundary layer, except for fluids (A) Having high viscosities (B) Moving at low velocities (C) Both (A) & (B) (D) Neither (A) nor (B)

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

__________ flow means the flow of incompressible fluid with no shear. (A) Potential (B) Streamline (C) Creep (D) Boundary layer

Description : __________ flow means the flow of incompressible fluid with no shear. (A) Potential (B) Streamline (C) Creep (D) Boundary layer

Last Answer : (A) Potential

Explain fluid - film lubrication with diagram.

Description : Explain fluid - film lubrication with diagram.

Last Answer : Fluid film lubrication:  i) It is carried out by introducing the liquid lubricants in between the moving or sliding surface. The lubricant film covers the irregularities of the sliding or moving surface ... like watches, clocks, guns, sewing machines, scientific instrument etc.  Diagram

Transmission of fluid in dentinal tubules is by: A. Hydrodynamic pressure (Osmotic) B. Mechanical

Description : Transmission of fluid in dentinal tubules is by: A. Hydrodynamic pressure (Osmotic) B. Mechanical

Last Answer : A. Hydrodynamic pressure (Osmotic)

Hydrostatic testing is to be performed with: a) Water. b) Kerosene. c) Another fluid provided, its viscosity is no greater than water. d) Any of the above.

Description : Hydrostatic testing is to be performed with: a) Water. b) Kerosene. c) Another fluid provided, its viscosity is no greater than water. d) Any of the above.

Last Answer : d) Any of the above.

When does the heat generated by fluid friction becomes appreciable compared to the heat transferred between the fluids? (A) At high fluid velocity (B) At low velocity (C) When fluid flows past a smooth surface (D) None of these

Description : When does the heat generated by fluid friction becomes appreciable compared to the heat transferred between the fluids? (A) At high fluid velocity (B) At low velocity (C) When fluid flows past a smooth surface (D) None of these

Last Answer : (A) At high fluid velocity

Two piping system are said to be equivalent, when the __________ are same. (A) Fluid flow rate & friction loss (B) Length & friction factor (C) Diameter & friction factor (D) Length & diameter

Description : Two piping system are said to be equivalent, when the __________ are same. (A) Fluid flow rate & friction loss (B) Length & friction factor (C) Diameter & friction factor (D) Length & diameter

Last Answer : (A) Fluid flow rate & friction loss