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Analysis of ISRO Mechanical Question Papers from 2006 to 2018 Average number of questions in each subject over each year Engineering Mathematics                                   - 8.2 (10.3%) Engineering Mechanics                                       - 7.9 (9.8%) Strength of Materials                                           - 11.2 (14.0%) Fluid Mechanics                                                  - 11.6 (14.5%) Thermal Engineering                                ...

            ISRO 2018 Mechanical Engineering Questions, Answers and Explanation 1. If the stream function of a two dimensional flow is Ψ = 5xy, then the velocity at a point (3,4) is a) 25 m/s b) 20 m/s c) 7 m/s d) 5 m/s Answer a) 25 m/s Explanation [ Fluid Mechanics ] u = ∂ Ψ/∂ y = 5x v =-  ∂ Ψ/∂ x = -5y At (3,4) u = 5x3 = 15 m/s At (3,4), v = -5x4 = -20 m/s Resultant velocity = √(15 2 +(-20) 2 )= 25 m/s 2. A glass tube of 8 mm diameter is immersed in water. Surface tension of water is 0.0075 kg/m and rise of water in the tube due to capillary effect is a) 7.5 mm b) 3.75 mm c) 11.25 mm d) none of these Answer b) 3.75 mm Explanation [ Fluid Mechanics ] Surface tension of the water tends to pull the water above the level and the weight of water tends to pull it back to its level. For water the angle between the surface tension force and plane of water is 90 o . Force due to surface tension = Weight of water above the level...

               ISRO 2008 Mechanical Engineering Questions, Answers and Explanation 38. In centrifugal pumps maximum efficiency is obtained when the blades are  a) Straight b) Bent forward c) Bent backward d) Radial Answer c) Bent backward Explanation [ Fluid Mechanics ] For fluids in in-compressible regime of operation such as water backward curved vanes are used for maximum efficiency. For radial and forward bent vanes the power requirement increases monotonically as the discharge increases. But for backward curved the power requirement peaks at maximum efficiency. 

ISRO 2007 Mechanical Questions, Answers and Explanation 1. Only rocket engines can be propelled to space because a) They can generate very high thrust b) They have high propulsion efficiency c) These engines can work on several fuels d) They are not air-breathing engines Answer d) They are not air-breathing engines Explanation [ Engineering Mechanics ] Even though all the choices are true, for travel in space the engines must use their own oxidizer. So they should not be dependent on air 2. The universal gas constant of a gas is the product of molecular weight of the gas and  a) Gas constant b) Specific heat at constant pressure c) Specific heat at constant volume d) None of the above Answer a) Gas constant Explanation  [ Thermal Engineering ] The value of universal gas constant is 8.314 J mol -1 K -1 . This when divided by the molecular weight of gas we get specific gas constant Molecular mass of air = 28.97 g/mol R air ...

ISRO Mechanical Engineering Fluid Mechanics Fluid Properties - Bulk modulus 2011. 10.  A liquid compressed in cylinder has a volume of 0.04 m 3  at 50kg/cm 2  and a volume of 0.039 m 3  at 150 kg/cm 2 . The bulk modulus of elasticity of liquid is a) 400 kg/cm 2 b) 40 x 10 6  kg/cm 2 c) 40 x 10 5  kg/cm 2 d) 4000 kg/cm 2 Answer d) 4000 kg/cm 2 Explanation The bulk elastic properties of a material determine how much it will compress under a given amount of external pressure. The ratio of the change in pressure to the fractional volume compression is called the bulk modulus of the material. The reciprocal of the bulk modulus is called the compressibility of the substance. Bulk Modulus, B = ΔP/(ΔV/V) Here ΔP = 150-50 =100 kg/cm 2 ΔV = 0.04-0.039 = 0.001m 3 V = 0.04m 3 B = (100/(0.001/0.04)) = 100x0.04/0.001 =  4000 kg/cm 2 Fluid Properties - Surface Tension 2011.13  If the surface tension of water-air interface ...

ISRO Mechanical Engineering Theory of Machines and Mechanical Vibrations Gear and Gear Trains 2014. 80 . Which type of gear meshing should be employed to transmit torque to a linear force? a) Epicyclic gear b) Helical gear c) Bevel gear d) Rack and pinion Answer d) Rack and pinion Explanation Epicyclic gear trains have one or more axes of gears in motion. In all other gear types the gear rotates about an axis but the axis does not move. Helical gears are smoother in operations and create a thrust load and hence required support to compensate this load. They can also be used to transmit torques at 90 o   Bevel gears are the ones in which the axes of gears intersect normally at 90 o . But they can work at other angles also. Rack and pinion gears are used to convert rotation into linear motion. 2017.2.8.  Which of the following is FALSE? a) A reverted gear train is one in which the first and last gears are on the same axis. b) Train value for a gear is ...

ISRO 2006 Mechanical Questions, Answers and Explanation Question Set A 1 . In nodular iron, graphite is in the form of      a) Cementite      b) Free Carbon      c) Flakes      d) Spheroids Answer d) Spheroids Explanation  [ Material Science ] Nodular cast iron is also called ductile cast iron or spheroidal graphite iron. As graphite is in the form of nodules they inhibit formation of cracks and hence more ductile. In grey cast iron where graphite is in the form of flakes exhibit more stiffness. On extension they create concentration points and hence are less ductile. Free carbon that is present in an elemental form is often an impurity which could be removed by smelting. Cementite is iron carbide with 6.67% Carbon by weight. 2 . Hardness of steel depends on      a) Amount of carbon it contains      b) The shape and distribution of of the carbides in the iron   ...

ISRO Mechanical Engineering Thermal Engineering Questions, Answers and Explanation System Properties 2007.2.  The universal gas constant of a gas is the product of molecular weight of the gas and a) Gas constant b) Specific heat at constant pressure c) Specific heat at constant volume d) None of the above Answer a) Gas constant Explanation The value of universal gas constant is 8.314 J mol -1 K -1 . This when divided by the molecular weight of gas we get specific gas constant Molecular mass of air = 28.97 g/mol R air  = 8.314x1000/28.97 J kg -1 K -1  = 287  J kg -1 K -1 . 2007.3.  Van der Waal's equation of state of a gas is a) pV = nRT b) (p+a/V 2,/sup>)(v+b) = RT c) (p+a/V 2,/sup>)(v-b) = RT d) (p-a/V 2,/sup>)(v-b) = RT Answer c) (p+a/V 2,/sup>)(v-b) = RT Explanation The constant 'a' provides correction for inter molecular forces and b for finite molecular size.  The effect of the finite volume of the particl...