MECHANICAL TECHNICAL INTERVIEW QUESTIONS WITH ANSWERS

MECHANICAL TECHNICAL INTERVIEW QUESTIONS WITH ANSWERS, FLUID MECHANICS INTERVIEW QUESTIONS

    FLUID MECHANICS
1381. A fluid is a substance that
a. always expands until it fills any container
b. is practically impressible
c. can’t be subjected to shear forces
d. can’t remain at rest under action of any shear force
e. has the same shear stress at a point regardless of its motion
1382. Newton’s law of viscosity relates
a. pressure, velocity & viscosity
b. shear stress and rate of angular deformation, in a fluid
c. shear stress, temperature, viscosity & velocity
d. pressure. viscosity & rate of angular deformation
e. yield shear stress, rate of angular deformation & viscosity
1383. An object has a mass of 2 kg & gravity force of 19 N on a spring balance. The value of gravity in m/s² is
a. 0.105 b. 2
c. 9.5 d. 19
e. none of the above
1384. An unbalanced force of 10 N exarted on 2 kg mass on a planet where g = 10 m/s²
a 0.2 b. 2
c. 5 d. 20
e. none of the above

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1385. The gravity force in Newton’s of 3 kg mass on a planet where g = 10 m/s² is
a. 0.3 b. 3.33
c. 29.42 d. 30
e. none of the above
1386. Viscosity has the dimensions
a. FL-2 b. FL-1T-1
c. FLT-2 d. FL2T
e. FTL-2
1387. Shear forces in a fluid
a. can never occur when the fluid is at rest
b. may occur due to cohesion when the liquid is at rest
c. depend upon molecular interchange of momentum
d. depend upon cohesive forces
e. can never occur in a frinctionless fluid, regardless of its motion
1388. The unit of dynamic viscosity is
a. m.s/kg b. N.m/s²
c. kg.s/N d. N.s/m2
1389. The dimensions of kinematic viscosity are
a. FL-2T b. ML-1T-1
c. L2T2 d. L2T-2
e. L2T-2
1390. For = 3 x 10-8 m²/s = 800 kg/m3, equals
a. 3.75 x 10-11 b. 2.4 x 10-5
c. 2.4 x 105 d. 2.4 x 1012
e. none of the above
1391. A perfect gas
a. has zero viscosity
b. has constant viscosity
c. is incompressible
d. satisfies P = RT
e. fits none of these
1392. The bulk modulus of elasticity for a gas at constant temperature to is given by
a. P b.RTo
c. PT d. PRTo
e. none of the above
1393. The bulk modulus of elasticity
a. is independent of temperature
b. increases with pressure
c. has the dimensions of l/p
d. is larger when the fluid is more compressible
e. is independent of pressure & viscosity
1394. The pressure centre is
a. at the centroid of the submerged
b. the centroid of the pressure prism
c. independent of the orientation of the area
d. a point on the line of action of the resultant force
e. always above the centroid of the area
1395. A vertical Tri-angular area has one side in a free surface, with vortex downward. Its altitude is h. The pressure centre is below the free surface
a. h/4 b. h/3
c. h/2 d. 2h/3
e. 3h/4
1396. A vertical gate 4m x 4m holds water with free surface at its top. The moment about the bottom of the gare is
a. 42.7r b. 57r
c. 64r d. 85.3r
e. none of the above
1397. A body floats in stable equilibrium
a. when its meta-centric height is zero
b. only when its centre of gravity is below the centre of buoyancy
c. when the meta-centre is above the centre of gravity
1398. When a liquid rotates at a constant angular velocity about a vertical axis as a rigid body, the pressure
a. decreases as the square of the radial distance
b. increases linearly as the radial distance
c. decreases as the square of increase in elevation along any vertical line
d. varies inversely as the elevation along any vertical line
e. varies as the square of the radial distance
1399. A forced vortex
a. turns in an opposite direction to a free vortex
b. always occurs in conjunction with a free vortex
c. has the velocity decreasing with radius
d. occurs when fluid rotates as a solid
e. has the velocity decreasing inversely with the radius
1400. Select the correct practical example of steady non-uniform flow
a. motion of water around a ship in a lake
b. motion of a river around bridge piers
c. steadily increasing flow through a piers
d. steadily reducing flow through a decreasing cross section

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1401. The assumptions made in deriving the equation gz + v2/2 + dp/p constant are
a. steady, frictionless, incompressible, along a stream line
b. uniform, frictionless, along a streamline, p-a function of P
c. steady, uniform, incompressible alonga streamline
d. steady, frictionless, p-a function of p, along a streamline
1401. The work that a liquid is capable of doing by virtue of its sustained pressure is
a. Z b. P
c. P/W d. V2/2g
e. 2gh
1402. The velocity head is
a. V2/2g b. Z
c. V d. 2gh
e. none of the above
1403. The kinetic energy correction factor
a. applies to the continuity equation
b. has the units of velocity head
c. is expressed by 1/A + v/V dA
d. is expressed by 1/A + (v/V)2 dA
e. is expressed by 1/A + (v/V)3 dA
1405. A pitot tube is used to measure velocity of flow of fluid of specific gravity 0.90. The fluid level inside the tube is 50 mm higher than the surface of flowing fluid. The velocity is(m/s)
a. 0.89 b. 0.99
c. 1.10 d. 1.40
e. none of the above
1406. The theoritical velocity of oil S=0.75 flowing from an orifice in a reservoir under a head of 4 ms is (in m/s)
a. 6.7 b. 8.86
c. 111.8 d. data insufficient
e. none of the above
1407. If all losses are neglected, the pressure at the summit of a siphon
a. is a minimum for the siphon
b. depends on height of summit above upstream reservoir
c. is independent of downstream length
d. is independent of discharge and density
1408. Select from the following list the correct assumptions for analyzing the flow of a jet that is deflected by a fixed/moving vane
1. The momentum of the jet is unchanged
2. The abs. speed doesn’t change along the vane
3. The fluid flows on the vane without shock
4. The flow from the nozzle is steady
5. Friction between jet and vane is neglected
6. The jet leaves without velocity
7. The velocity is uniform over the C.S of the jet
a. 1,3,4,5 b. 2,3,5,6
c. 3,4,5,6 d.3,4,5,7
e. 3,5,6,7
1409. The losses due to sudden expansion is
a. (V12-V22)/2g b. (V1 V2 )/2g
c. (V22-V12)/g d. (V1-V2)2/g
e. (V1-V2)2/2g
1410. Reynolds number may be defined as the ratio of
a. viscous to inertia forces
b. viscous to gravity forces
c. gravity to inertia forces
d. elastic to pressure forces
e. none of the above
1411. The shear stress in a fluid flowing between two fixed parallel plates
a. is constant over the cross-section
b. is ‘O’ at the plates and increases linearly to mid point
c. varies parabolically across the section
d. is‘O’ at the midplane and is linear variant from mid plane
e. none of the above
1412. The velocity distribution for flow between two fixed parallel plates is
a. uniform over the C.S
b. ‘O’at the plates and increases linearly to mid plane
c. varies parabolically over the C.S
1413. The relation between pressure and shear stress in laminar flow in x direction is
a. .p/.x = c/y
b. OP/OY = 1/x
c. p/y = 1/x
d. p/x = 1/y
1414. The shear stress in a fluid flowing in a round pipe
a. is constant over the C.S
b. is zero at the wall and increases linearly to the centre
c. varies parabolically across the section
d. is zero at the centre and varies linearly with radius
1415. In laminar flow through round tube the discharge varies
a. linearly as viscosity
b. as square of radius
c. inversely as pressure drop
d. inversely as viscosity
e. as cube of diameter
1416. The upper critical Reynold’s No. is
a. important from design view point
b. the number at which turbulent flow changes to laminar flow
c. about 2000
d. not more than 2000
e. none of the above
1417. Reynold’s No. for pipe flow is given by
a. VD/C
b. VD/P
c. VDP/T
d. VD/K
e. none of the above
1418. The lower critical Reynold’s No. has the value
a. 200
b. 1200
c. 12000
d. 40000
e. none of the above
1419. The hydraulic radius is given by
a. wetted perimeter divided by area
b. area perimeter divided square of wetted
c. square root of area
d. area divided by wetted perimeter
e. none of the above
1420. The hydraulic radius of a 60 mm wide by 120 mm deep open channel is in mm
a. 20
b. 24
c. 40
d. 60
e. none of the above
1421. The friction factor in turbulent flow in smooth pipes depends on
a. V,D,P,L
b. Q,L,P
c. V,D,P,P
d. V,D,P
e. P,L,D,Q,V

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