ISRO Scientist or Engineer Mechanical 2020

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ISRO Scientist or Engineer Mechanical 2020 - Question 1

A centrifugal pump havingan impeller diameterof 127 mm,delivers a powerof 12 hp. If the impesrer Giameter is changed to 254 mm, what is the power, if other parameters are kept constant?

ISRO Scientist or Engineer Mechanical 2020 - Question 3

An open tankis filled with waterto a height of 20m. Whatis the velocity of the water flow at the outlet, if the outlet is at the base of the tank?

ISRO Scientist or Engineer Mechanical 2020 - Question 5

An experiment is conducted with a fluid of density 1 $$\frac{kg}{m^{3}}$$ at 10 $$\frac{m}{s}$$ velocity. The free stream static pressure is 100 kPa and the local static pressure is 101 kPa. What is thepressure coefficient at the location?

ISRO Scientist or Engineer Mechanical 2020 - Question 10

Which of the following can be used to determine the variation of saturation pressure with temperature along phase boundaries?

ISRO Scientist or Engineer Mechanical 2020 - Question 11

Air at $$27 ^\circ$$C and 100 kPa enters in a steady flow to a nozzle at a velocity of 100 $$\frac{m}{s}$$. If theinlet area of the nozzle is 0.5 $$m^{2}$$, what is the mass flow rate through the system

ISRO Scientist or Engineer Mechanical 2020 - Question 13

In a shower mixer, cold water at 27 deg C, flowing at 5 kg/min is mixed with hot water at 77 deg C flowing at 15 kg/min.The exit temperature of the mixture is

ISRO Scientist or Engineer Mechanical 2020 - Question 16

A gas is containedin a cylinder with a moveable piston of 100 kg mass. When 2500 J of heat flows into the gas, the internal energy of the gas increases by 1500 J. Whatis the distance through which the piston rises?

ISRO Scientist or Engineer Mechanical 2020 - Question 17

A refrigerator with COP of 6 is used in a room at 300 K. Whatwill be the heat intake through a section of refrigerator wall of area $$100 cm \times 100 cm$$ with a thickness of 10 cm assuming only conduction? Value of thermal conductivity of the wall can be taken as 1 $$\frac{W}{cm}$$.K

ISRO Scientist or Engineer Mechanical 2020 - Question 18

A Mass of 1Kg of air at $$27^\circ$$ and 0.98 atm is taken through a diesel Cycle. If the compression ratio of the the engine is 16,calculate the temperature of the air after compression ?(for calculation, take the ratio of the specific heats of air as 1.5)

ISRO Scientist or Engineer Mechanical 2020 - Question 19

An aircraft is in its take off roll at sea level with ambient temperature of 18°C. What is the approximate speed of the aircraft if the temperature measured by a probe at the exist of the engine diffuser is $$36^\circ$$ C? (Assuming air Stagnation at diffuser outlet and $$C_{p}$$ of air as 1.0 $$\frac{kJ}{Kg.K}$$)

ISRO Scientist or Engineer Mechanical 2020 - Question 20

The external surface of a wall of height 3m height ,5 m width and 0.5 m thickness is at a temperature of $$2^\circ$$ C.If a heat loss of 150 wfrom the room is measured across the wall ,find the inner wall temperature ?The thermal conductivity of wall material can be taken as 1 $$\frac{W}{m.k}$$

ISRO Scientist or Engineer Mechanical 2020 - Question 24

A fluid passes through a well insulated tube of $$4.7 cm^{2}$$ cross section area and 5 m length.If the pipe friction coefficient is 0.07 and the flow velocity is 3 $$\frac{m}{s}$$, then the flow can be represented using?

ISRO Scientist or Engineer Mechanical 2020 - Question 25

A fluid having a density of 1 $$\frac{g}{cc}$$ is in a state with Grashof number $$2 \times 10^{6}$$ and prandtl number 0.7. Assuming acceleration due to gravity as 10 $$\frac{m}{s^{2}}$$, calculate the Rayleigh number?

ISRO Scientist or Engineer Mechanical 2020 - Question 26

A cold liquid enters a counter flow heat exchanger at 15 deg at a rate of 8 $$\frac{kg}{s}$$. A hot stream of the same liquid enters the heat exchanger at 7 deg at 2 $$\frac{kg}{s}$$ Assuming the specific heat of the fluid as 4 $$\frac{kJ}{kg}.^\circ$$C, determine the maximum heat transfer rate.

ISRO Scientist or Engineer Mechanical 2020 - Question 27

The temperature of a surface with $$0.2 m^{2}$$ area is 17 deg C.Calculate the wavelength corresponding to maximum monochromatic emissive power

ISRO Scientist or Engineer Mechanical 2020 - Question 28

For a surface, the direct and diffuse components of the solar radiation are 400 and 300 $$\frac{W}{m^{2}}$$ and the direct radiation makes 60 deg angle with the normal .If the surface temperature is 300 K and effective sky temperature is 200 K , Calculate net rate of radiation of heat transfer .(Assume solar absorptivity and emmissivity as 0.1 each;For calculation take Stefan Boltzmanns constant as G \times 10^{-8} $$\frac{W}{m^{2}}.K^{4}$$)

ISRO Scientist or Engineer Mechanical 2020 - Question 29

Which of the following element is added to High Speed Tool Steels as a scavengerto remove slag impurities during melting and also for increasing cutting efficiency of tools.

ISRO Scientist or Engineer Mechanical 2020 - Question 31

‘The state of stress during deep drawing forming operation of a cup is

ISRO Scientist or Engineer Mechanical 2020 - Question 32

During turning of a metallic rod at a given condition, the tool life was founded to decrease from 100 min. to 25 min. ool if: cutting speed was increased from 50 $$\frac{m}{min}$$ How muchwill be life of tool if the machined at 80$$\frac{m}{min}$$?

ISRO Scientist or Engineer Mechanical 2020 - Question 33

In a single pass rolling operation, the thickness of a 100 mm wideplate is reduced from 20 mm to 15 mm. The roller radius is 125 mm and rotational speed is 8 rpm. The average
flow stress for the plate material is 400 Mpa.The power required for rolling operation in kW is?

ISRO Scientist or Engineer Mechanical 2020 - Question 36

In an arc welding process,two weld coupons were made using two different welding processes. For the first coupon, the voltage, current and welding speed used are 15 V, 300A
and 30 $$\frac{mm}{min}$$ respectively. Whereas the second couponis welded with 60 kV, 200 mA and 25 $$\frac{mm}{s}$$. If the heat transfer efficiency for welding the first coupon is half of that of second coupon, the ratio of heat input per unit lengthis?

ISRO Scientist or Engineer Mechanical 2020 - Question 37

In Gas tungsten arc welding (GTAW) which of the following polarity is generally used for getting higher penetration

ISRO Scientist or Engineer Mechanical 2020 - Question 38

The laws of adhesive wear, commonly referred to as Archard's law can be expressed as ..................
(If ‘Q’ is the total volume of wear debris produced, ‘W’ is the normal load, ‘L’ is the sliding distance, ‘H’ is the hardness of the softest contacting surfaces being worn away, and ky’is a
non-dimensional wearcoefficient dependent on the materials in contact and their exact degree of cleanliness)

ISRO Scientist or Engineer Mechanical 2020 - Question 39

Ina four-barlinkageif ‘S’ is the length of the shortest link, ‘L’ is the length of longestlink and ‘P’ & ‘Q’ are lengthofotherlinks, then the criteria for getting a triple rocker mechanism in which no links will fully rotate is.

ISRO Scientist or Engineer Mechanical 2020 - Question 40

The piston of an engine moves with simple harmonic motion. The crank rotates at 120 r.p.m with a stroke of 2 meters. The velocity of the piston, when it is at a distance of 0.8 metre from the center is.

ISRO Scientist or Engineer Mechanical 2020 - Question 41

If a block slides outward on a link at a uniform rate of 30 $$\frac{m}{s}$$, while the link is rotating at a constant angular velocity of 50 $$\frac{rad}{s}$$ counter clockwise, the Coriolis component of acceleration is ................$$ \frac{m}{sec^{2}}$$.

ISRO Scientist or Engineer Mechanical 2020 - Question 42

In a screw jack of lead angle a, the effort required to lift the load Wis given by ........... ($$\phi$$ = Friction Angle)

ISRO Scientist or Engineer Mechanical 2020 - Question 44

A disc spinning on its axis at 20 $$\frac{rad}{s}$$ will undergo precession when a torque 100 N-m is applied about an axis normal to it. If the mass momentof inertia is 1 kg-m?, then the angularvelocity of precession is?

ISRO Scientist or Engineer Mechanical 2020 - Question 54

What does ‘a’ and ‘e’ indicate in the surface texture symbol shown below

ISRO Scientist or Engineer Mechanical 2020 - Question 56

A block weighing 100 N is resting on a plane inclined with horizontal as shown in Fig. What horizontal force P is necessary to hold the body from sliding down the plane? (Coefficient of friction can be taken as 0.25)

ISRO Scientist or Engineer Mechanical 2020 - Question 59

Steel machine element at the critical section is in biaxial stress state with two principal stress being 300 $$\frac{N}{mm^{2}}$$ and 300 $$\frac{N}{mm^{2}}$$ (equal magnitude). Find the von Mises stress (in $$\frac{N}{mm^{2}}$$) in the member

ISRO Scientist or Engineer Mechanical 2020 - Question 60

A machine component of 90 kg mass needs to be held in position using three springs as shown below .The spring constants K_{1}, K_{2},K_{3} are 4,4 and 8 $$\frac{N}{m}$$ respectively. Find the natural freqeuncy of the system in $$\frac{rad}{sec}$$.

ISRO Scientist or Engineer Mechanical 2020 - Question 61

A cylindrical pressure vessel has diameter 200 mm and thickness 9 mm. Find the hoop and axial stress $$(\frac{N}{mm^{2}})$$ in the cylindrical vessel, when it is subjected to an internal pressure of 5 MPa.

ISRO Scientist or Engineer Mechanical 2020 - Question 63

If the length of a column subjected to compressive load is increased by three times its original length, the critical buckling load becomes

ISRO Scientist or Engineer Mechanical 2020 - Question 64

A squarebar of size $$10mm \times 10 mm$$ and length 1000 mmis subjected to 200 N axialtensile force. The bar is made of mild steel having modulusofelasticity of 200 GPa. Find the strain energy density stored in the bar underthis state of loading?

ISRO Scientist or Engineer Mechanical 2020 - Question 65

A solid circular shaft needs to be designed to transmit a torque of 55 N m. If the allowable shearstress of the material is 280 $$\frac{N}{mm^{2}}$$ ind the diameter (in mm)of the shaft required tO transmit the torque. $$(Assume,\pi=\frac{22}{7})$$

ISRO Scientist or Engineer Mechanical 2020 - Question 66

If S is the applied stress, c 1s the width of the crack and r the radius of curvature at the tip of the crack, Griffith's crack theory gives the concentrated stress $$S_{c}$$ as

ISRO Scientist or Engineer Mechanical 2020 - Question 67

A metal alloy machine component is subjected to fluctuating tensile stress from 100 $$\frac{N}{mm^{2}}$$ to 200 $$\frac{N}{mm^{2}}$$. The material has yield and endurance strength of 450 and 200 $$\frac{N}{mm^{2}}$$ respectively. Find the factor of safety of the machine component.

ISRO Scientist or Engineer Mechanical 2020 - Question 68

A diver of mass 100kg is standing at the tip of a spring board of negligible mass. The natural frequency of the spring board with the diver is 1.6Hz. Whatis the static deflection at the tip of the spring board whenthe diveris standing at the tip?

ISRO Scientist or Engineer Mechanical 2020 - Question 76

If $$K_{f}$$ is the fatigue stress concentration factor and $$K_{t}$$ is the theoretical stress concentration factor then, the notch sensitivity q is?

ISRO Scientist or Engineer Mechanical 2020 - Question 79

The natural frequency of a simply supported beam of length l with mass M at its centre , flexual rigidity EI and negligable beam mass is

ISRO Scientist or Engineer Mechanical 2020 - Question 80

A machine component of natural frequency 200 $$\frac{rad}{s}$$ is Subjected to a base motion from the machine which is harmonic in nature with amplitude 3 $$\frac{m}{s^{3}}$$ at $$\frac{rad}{sec}$$ Whatis the peak amplitude of relative displacement of the components if the damping is negligable

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