ISRO Mechanical-Engineering Contributed by Theertha updated on Jun 2019

ISRO mechanical engineering model questions for practice 

ISRO Fluid Mechanics question for practice

1.    Pascal-second is the unit of a)    pressure b)    kinematic viscosity c)    dynamic viscosity d)    surface tension Ans: c   2.    An ideal fluid is a)    one which obeys Newton's law of viscosity b)    frictionless and incompressible c)    very viscous d)    frictionless and compressible Ans: b   3.    The unit of kinematic viscosity is a)    gm/cm-sec2 b)    dyne-sec/cm2 c)    gm/cm2-sec d)    cm2/sec Ans: d   4. If the dynamic viscosity of a fluid is 0.5 poise and specific gravity is 0.5, then the kinematic viscosity of that fluid in stokes is a)    0.25 b)    0.50 c)    1.0 d)    none of the above Ans: c   5.     The viscosity of a gas a)    decreases with increase in temperature b)    increases with increase in temperature c)    is independent of temperature d)    is independent of pressure for very high pressure intensities Ans: b   6.       Newton's law of viscosity relates a)    intensity of pressure and rate of angular deformation b)    shear stress and rate of angular deformation c)    shear stress, viscosity and temperature d)    viscosity and rate of angular deformation Ans: b   7.    An open tank contains 1 m deep water with 50 cm depth of oil of specific gravity 0.8 above it. The intensity of pressure at the bottom of tank will be a)    4 kN/m2 b)    10 kN/m2 c)    12 kN/m2 d)    14 kN/m2 Ans: d   8.    The position of center of pressure on a plane surface immersed vertically in a static mass of fluid is a)    at the centroid of the submerged area b)    always above the centroid of the area c)    always below the centroid of the area d)    none of the above Ans: c   9.     The total pressure on a plane surface inclined at an angle 9 with the horizontal is equal to a)    PA b)    pA sin 9 c)    pA cos 9 d)    pA tan 9 where p is pressure intensity at centroid of area and A is area of plane surface. Ans: a   10. A vertical rectangular plane surface is submerged in water such that its top and bottom surfaces are 1.5 m and 6.0 m res-pectively below the free surface. The position of center of pressure below the free surface will be at a distance of a)    3.75 m b)    4.0 m c)    4.2m d)    4.5m Ans: c   11.    Centre of buoyancy always a)    coincides with the centre of gravity b)    coincides with the centroid of the volume of fluid displaced c)    remains above the centre of gravity d)    remains below the centre of gravity Ans: b   12.    If the weight of a body immersed in a fluid exceeds the buoyant force, then the body will a)    rise until its weight equals the buoyant force b)    tend to move downward and it may finally sink c)    float d)    none of the above Ans: b   13.    Metacentric height for small values of angle of heel is the distance between the a)    centre of gravity and centre of buoy-ancy b)    centre of gravity and metacentre c)    centre of buoyancy and metacentre d)    free surface and centre of buoyancy Ans: b   14. A floating body is said to be in a state of stable equilibrium a)    when its metacentric height is zero b)    when the metacentre is above the centre of gravity c)    when the metacentre is below the centre of gravity d)    only when its centre of gravity is below its centre of buoyancy Ans: b   15.   The increase in meta centric height  i)    increases stability  ii)   decreases stability  iii) increases comfort for passengers  iv) decreases comfort for passengers  The correct answer is  a)    (i) and (iii) b)    (i)and(iv) c)    (ii) and (iii) d)    (ii) and (iv) Ans: b   16. A rectangular block 2 m long, 1 m wide and 1 m deep floats in water, the depth of immersion being 0.5 m. If water weighs 10 kN/m3, then the weight of the block is a)    5kN b)    lOkN c)    15 kN d)    20 kN Ans: b   17.    The point in the immersed body through which the resultant pressure of the liquid may be taken to act is known as a)    center of gravity b)    center of buoyancy c)    center of pressure d)    metacentre Ans: c   18.    If a vessel containing liquid moves downward with a constant acceleration equal to 'g' then a)    the  pressure  throughout the  liquid mass is atmospheric b)    there will be vacuum in the liquid c)    the pressure in the liquid mass is greater than hydrostatic pressure d)    none of the above Ans: a   19.    When a liquid rotates at a constant angular velocity about a vertical axis as a rigid body, the pressure intensity varies a)    linearly with radial distance b)    as the square of the radial distance c)    inversely as the square of the radial distance d)    inversely as the radial distance Ans: b   20.    An open cubical tank of 2 m side is filled with water. If the tank is rotated with an acceleration such that half of the water spills out, then the acceleration is equal to a)    g/3 b)    g/2

c)    2g/3

d)    g

Ans: d

 

1 What is the difference between isotropic and anisotropic materials?


Ans If a material exhibits same mechanical properties regardless of loading direction, it is isotropic eg., homogeneous cast materials. Materials lacking this property are anisotropic

2    What are orthotropic materials

It is a special class of anisotropic materials which can be described by giving their properties in three perpendicular direction et wood composites

3    A plain carbon steel has BHN of 180 What are values of Rc,  VHN and ultimate strength?

Ans Rc-RHN/10  18,VHN BHN 180

4    What properties need to be considered for applications calling for following requirement:

irigdity

strength for no plastic deformation under static load

wear resistance

reliability and safety

Ans Rigidity- elastic modules and yield strength

Strength for no plastic deformation under static loading-yield point

Wear resistance-Hardness

Reliability and safety-Endurance limit and yield point

5     Explain the effects of alloying chromium and nickel in stainless steel.

Addition of nickel and chromium increases the tensile strength and increase in resistance to corrosion takes place.

6    Mention two types of dislocation'

Dislocation refers to a break in the continuity of the lattice. In edge dislocation, one place of atoms gets squeezed out.In screw dislocation the lattice atoms move from their regular ideal positions.

7    What are the principal constituents of brass?

Principal constituents of brass are copper and zinc

8 what is curie point?

Curie point is te temperature at which ferromagnetic materials can no longer be magnetized by outside forces

9 Specific strength of materials is very high when they are in fiber size but lower when they are in bar form-Why?

Crystal structure has ordered, repeating arrangement of atoms, fibers are liable to maintain this and thus have high specific strength. As size increases, the condition of ordered and repeating arrangements cant be guaranteed because of several types of defects and dislocations and thus the specific strength gets lower

10    what is the percentage of carbon in cast iron?

2.5%

11     Which element is added in steel to increase resistance to corrosion?

Chromium

12     whether individual component material retain their characteristics or not 

Yes

13    An elastomer is a polymer when its percentage elongation rate is

Greater than 100%

14    If % elongation of material is more tha  200% it is classed as

Rubber

15    Why is it that the maximum value which the residual stress can reach is the elastic limit of the material?

A stress in excess of elastic limit with no external force to oppose it will relieve itself by plastic deformation until it reaches the value of the yield stress

 

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