Quiz: Mechanical Engineering 9th July 2020

Quiz: Mechanical Engineering
Exam: UPPSC AE
Topic: Miscellaneous

Each question carries 3 mark.
Negative marking: 1 mark
Time: 10 Minute

Q1. In regarding nucleate boiling ___________
(a) The temperature of the surface is greater than the saturation temperature of the liquid
(b) Bubbles are created by expansion of entrapped gas or vapour at small cavities in the surface
(c) The temperature is greater than that of film boiling
(d) All options are correct

Q2. Calculate the power (in kW) required by the engine of a car travelling at the constant speed of 50 m/s. If the car has to resist a wind drag F_D=20V(in N), where V is the velocity of the car.
(a) 20
(b) 25
(c) 50
(d) 75

Q3. Water, by evaporating cooling, can be theoretically be cooled down to
(a) Atmospheric temperature
(b) Air dry bulb temperature
(c) Air wet bulb temperature
(d) Air dew point temperature

Q4. What is the location of frictional force when the intensity of pressure is uniform in a flat pivot bearing having radius r?
(a) r
(b) r/2
(c) 2r/3
(d) r/3

Q5. When the depth of water in an open channel is less than the critical depth, then flow is said to be
(a) critical
(b) turbulent
(c) torrential
(d) tranquil

Q6. In order that no shock wave develops when flow is taking place through a converging-diverging tube, Mach number at exit should be
(a) equal to 1
(b) greater than 1
(c) less than 1
(d) none of these

Q7. Which of the following is the correct method for the conversion of spring-controlled governor from unstable to stable?
(a) Increasing the ball weight
(b) Decreasing the spring stiffness
(c) Decreasing the ball weight
(d) Increasing the spring stiffness

Q8. Which one of the following assumptions in the theory of pure torsion is false?
(a) The angle of twist is uniform along the length
(b) The shaft is of uniform circular section throughout
(c) Cross-section plane before torsion remains plane after torsion
(d) All radii get twisted due to torsion

Q9. Filling or decking in a cooling tower increases the rate of heat transfer by providing
(a) increased flow of water
(b) increased flow of air
(c) increased flow of water and air
(d) a large amount of wetted surface

Q10. Two-stroke engines are used more frequently in two wheelers due to which of the following reasons?
(a) exhaust is less
(b) higher thermal efficiency
(c) higher power to weight ratio
(d) less friction

Solutions

S1. Ans.(a)
Sol. Nucleate boiling is a type of boiling that takes place when the surface temperature is hotter than the saturated fluid temperature by a certain amount but where the heat flux is below the critical heat flux.

S2. Ans.(c)
Sol. We know that
Power required = F_D×V
= 20×V×V
= 20×50^2
= 50 kW

S3. Ans.(c)
Sol. By evaporating cooling, air can be cooled down to its wet bulb temperature. Evaporative cooling is a process that uses the effect of evaporation as a natural heat sink. Sensible heat from the air is absorbed to be used as latent heat necessary to evaporate water.

S4. Ans.(c)
Sol. The frictional force acts at 2r/3 distance from the center when intensity of pressure is given uniform.

S5. Ans.(c)
Sol. When the depth of water in an open channel is less than the critical depth, then flow is said to be torrential.

S6. Ans.(b)
Sol. Mach number at exit should be greater than 1 for no shock wave generation when flow is taking place through a converging-diverging tube.

S7. Ans.(b)
Sol. A spring-controlled governor is said to be stable if the radius of the balls increases with increase in the speed of the governor and vice versa. A spring-controlled governor can be made stable by decreasing the spring stiffness.

S8. Ans.(a)
Sol. Following assumptions are made in the theory of pure torsion:
The material of shaft is uniform throughout
The shaft is of uniform circular cross-section throughout its length
Cross section remains plane before and after torsion.
All radii get twisted due to torsion

S9. Ans.(d)
Sol. Filling or decking in a cooling tower increases the rate of heat transfer by providing increased wetted area.

S10. Ans.(c)
Sol. Two-stroke engines are used more frequently in two wheelers due to higher power to weight ratio of these engines.

Quiz: Mechanical Engineering 2 June 2020

Quiz: Mechanical Engineering
Exam: ISRO
Topic: Material science

Each question carries 1 mark
Negative marking: 1/3 mark
Time: 10 Minutes
Q1. Atoms are arranged in face centred cubic (FCC) structure as
(a) All eight corners of the cube
(b) All eight corners of the cube and one of the body center
(c) All eight corners of the cube and at the center of each face
(d) All eight corners of the cube and one at the body center with one at the center of each face

Q2. Which of the following are zero dimensional defects?
1. Vacancy
2. Interstitial defect
3. Substitutional defect
(a) 1 and 2 only
(b) 1 and 3 only
(c) 2 and 3 only
(d) 1, 2 and 3

Q3. The number of electrons found in the outer most orbit of semi-conductor materials is,
(a) 2
(b) 4
(c) 6
(d) 8

Q4. What is the packing factor of FCC crystal structure?
(a) 0.64
(b) 0.68
(c) 0.74
(d) 0.78

Q5. Which is false statement about annealing?
(a) Annealing is done to relieve stresses
(b) Annealing is done to harden steel slightly
(c) Annealing is done to improve machine characteristics
(d) Annealing is done to soften material

Q6. Pearlite is a combination of:
(a) Ferrite and cementite
(b) Cementite and gamma iron
(c) Ferrite and austenite
(d) Ferrite and iron graphite

Q7. The Burger’s vector lies parallel to the dislocation line along the axis of a line of atoms in the same plane in:
(a) Screw dislocation
(b) Edge dislocation
(c) Cracks
(d) Vacancies

Q8. The atomic bond found in diamond is:
(a) Ionic
(b) Covalent
(c) Metallic bond
(d) None of these

Q9. Carbon content is highest in:
(a) Mild steel
(b) Eutectoid steels
(c) Hypoeutectoid steels
(d) Hypereutectoid steels

Q10. Which of the following is non-destructive test
(a) tensile test
(b) charpy test
(c) cupping test
(d) radiography test

S1. Ans(c)
Sol. Atoms are arranged in face centred cubic structure as all eight corners of the cube and at the centre of each face.

S2. Ans(d)
Sol. Defects in metal
(1) Point defect or zero dimensional defect
(a) Vacancy defect
(b) Interstitial defect
(c) Substitutional defect
(d) Frankle defect
(e) Schottky defect
(2) Surface defect
(a) Grain boundary defect
(b) Twin boundary defect
(c) Tilt boundary defect
(d) Staking faults
(3) Line defect
(a) Edge dislocation defect
(b) Screw dislocation defect

S3. Ans(b)
Sol. The number of electrons found in the outer most orbit of semi-conductor materials is 4.

S4. Ans(c)
Sol. Type of cell Packing factor
Simple cubic (SC) – 0.52
Hexagonal Close packed (HCP) – 0.74
Body centered cubic (BCC) – 0.68
Face-centered cubic (FCC) – 0.74

S5. Ans(b)
Sol. Annealing reduces the hardness of the steel completely and improve toughness, it is complete softening process and increase ductility.

S6. Ans(a)
Sol. Pearlite consists of 87% ferrite (layer are thick) and 13% cementite (thin layer) arranged alternatively in a lamelle formation.

S7. Ans(a)
Sol. Screw dislocation:- When a part of Crystal displaced angularly over the remaining about some edge, the dislocation is called screw dislocation.
(i) Burger’s vector is parallel to the screw dislocation line, whose direction is perpendicular.
(ii) Screw dislocation creates shear stress and strain in the crystal.

S8. Ans(b)
Sol. The atomic bond found is diamond is covalent bond.
Covalent Bond:- It is also called homopolar bond. This bond result by mutual sharing of valence electrons of identical atoms. The electronic structure of an atom is relatively stable it has eight electrons in its outer valence shell, which sometimes an atom acquires by shearing electrons with an adjacent similar atom. Diamond, methane chlorine are typical examples.

S9. Ans(d)
Sol. Carbon content is highest in hypereutectoid steels.

S10. Ans(d)
Sol. radiography test is the non-destructive test. In the radiography test there is no role of force so there is no deformation takes place within the testing material.
After the testing material is able to perform its functionality without any kind of destruction.

Quiz: Mechanical Engineering 26 May 2020

Quiz: Mechanical Engineering
Exam: ISRO TECHNICAL ASSISTANT
Topic: Miscellaneous

Each question carries 1 mark
Negative marking: 1/3 mark
Time: 10 Minutes

Q1. Autofrettage is a method of
(a) joining thick cylinders
(b) Reliving stresses from thick cylinders
(c) Prestressing thick cylinders
(d) Increasing the life of thick cylinders

Q2. In circular arc cam with a flat faced reciprocating follower, the contact between the
follower and the nose of cam is only maintained if :
(a) External spring force is less than the inertia force of the follower
(b) External spring force is greater than the inertia force of the follower
(c) External spring force is zero
(d) The inertia force is more than the spring force

Q3. A governor is said to be isochronous when the equilibrium speed is
(a) variable for different radii of rotation of governor balls
(b) constant for all radii of rotation of the balls within the working range
(c) constant for particular radii of rotation of governor balls
(d) constant for only one radius of rotation of governor balls

Q4. The effect of increasing the stiffness of springs of centrifugal clutch is
(a) The decrease of engagement speed
(b) The increase of engagement speed
(c) The increase of frictional force at maximum speed
(d) None of the above

Q5. The saturation temperature of steam with increase in pressure increase
(a) linearly
(b) rapidly first and then slowly
(c) slowly first and then rapidly
(d) inversely

Q6. Carbonization of coal is the process of
(a) pulverizing coal in inert atmosphere
(b) heating wood in a limited supply of air at temperatures below 300°C
(c) strongly heating coal continuously for about 48 hours in the absence of air in a
closed vessel
(d) binding the pulverized coal into brackets

Q7. Superheating of steam is done at
(a) constant volume
(b) constant temperature
(c) constant pressure
(d) constant entropy

Q8. Fluid is a substance that
(a) cannot be subjected to shear forces
(b) always expands until it fills any container
(c) has the same shear stress at a point regardless of its motion
(d) cannot remain at rest under action of any shear force.

Q9. Match List-I with List-II and select the correct answer using the code given below the lists:
List – I
Heat exchangers
Turbulent flow
Free convection
Radiation heat transfer
List–II
View factor
Effectiveness
Nusselt number
Eddy diffusivity
Codes
A B C D
(a) 3 1 2 4
(b) 2 4 3 1
(c) 3 4 2 1
(d) 2 1 3 4

Q10. Specific speed of a fluid machine
(a) refers to the speed of a machine of unit dimensions
(b) is a type-number representative of its performance
(c) is specific to the particular machine
(d) depends only upon the head under which the machine operates

SOLUTIONS

S1. Ans.(c)
Sol. Autofrettage: It is one of the oldest methods of prestressing (method of increasing pressure capacity) the cylinders. It is overloading the cylinder before it is put into service. In this method, a forged cylinder is subjected to a large internal pressure, so as to expand the internal diameter, causing overstrain. The internal pressure is applied is such a way that a portion of the cylinder at the inner surface is subjected to stresses in the plastic range. When the pressure is released, the portion of the cylinder at the outer surface contracts exerting the pressure on the portion at the inner surface which has undergone permanent deformation. As a result residual compressive stresses are induced at the inner surface and tensile stresses at the outer surface.
It is commonly used to gun barrels. It not only increases the pressure capacity of the cylinder, but also improves the endurance strength.

S2. Ans.(b)
Sol. When the cam contact force goes to zero, the cam and follower will separate. Large enough spring force is necessary to keep cam and follower in contact throughout the entire rotation. External spring force should be greater than inertia force of the follower to maintain positive contact. If external spring force is too large, there is possibility of higher contact stress leading to surface failure.

S3. Ans.(b)
Sol. Isochronous governor is a governor that keeps the speed of a prime mover constant at all loads. Also known as a static governor. A governor is said to be isochronous if equilibrium speed is constant for all the radii of rotation in the working range. Therefore, for an isochronous governor the speed range is zero and this type of governor shall maintain constant speed.

S4. Ans.(b)
Sol. When the load is released from clutch lever, it again engages with the shaft. As the stiffness of spring will increases, the restoring force on clutch will increase and hence velocity of engagement will be more.

S5. Ans (b)
Sol. At atmospheric pressure the saturation temperature is 100°C. However, if the pressure is increased, this will allow the addition of more heat and an increase in temperature without a change of phase. Therefore, increasing the pressure effectively increases both the enthalpy of water, and the saturation temperature.

S6. Ans (c)
Sol. Coal carbonization is used for processing of coal to produce coke using metallurgical grade coal. Coal carbonization involves heating of coal in the absence of air.

S7. Ans (c)
Sol. Superheated steam is a steam at a temperature higher than its vaporization (boiling) point at the absolute pressure where the temperature is measured

S8. Ans (d)
Sol. A fluid is a substance that continuously deforms under an applied shear force.

S9. Ans.(b)
Sol.
(a) Heat exchangers : Effectiveness
(b) Turbulent flow : Eddy diffusivity
(c) Free convection : Nusselt number
(d) Radiation heat transfer : View factor

S10. Ans (b)
Sol. Specific speed is of a fluid machine is a type number representative of its performance.
In order to compare the performance of different pumps, it is necessary to have some term which will be common to all the centrifugal pump the term ordinarily used for this purpose is the specific speed. This is a type characteristic and can be used to predict the behavior of one pump based on tests of similar, but different sized pumps.
The specific speed is a characteristic of pumps which can be used as basis for comparison of the performance of different pump.

Quiz: Mechanical Engineering 22 May 2020

Quiz: Mechanical Engineering
Exam: NLC GET
Topic: Miscellaneous
Each question carries 1 mark
Negative marking: 1/3 mark
Time: 10 Minutes

Q1. The maximum force which acts on the connecting rod is
(a) Force due to gas pressure
(b) Force due to inertia of piston
(c) Force due to friction of connecting rod
(d) Force due to crank pin

Q2. Strain rosettes are generally used for
(a) measurement of load
(b) measurement of shear strain
(c) measurement of longitudinal strain
(d) measurement of resilience

Q3. Toggle mechanism have following applications except
(a) Stone crushers
(b) Gear cutting
(c) Embossing presses
(d) Switches

Q4. Match the following List-I and List-II and select the correct answer using the codes
given below the lists:
List-I
A. Pantograph
B. Single slider crank chain
C. Double slider crank chain
D. Straight line motion
List-II
1. Scotch yoke mechanism
2. Double lever mechanism
3. Tchebicheff mechanism
4. Double crank mechanism
5. Hand pump
Codes:
A B C D
(a) 4 3 5 1
(b) 2 5 1 3
(c) 2 1 5 3
(d) 4 5 2 1

Q5. The delay period in CI engine depends upon
1. Temperature and pressure in the cylinder at the time of injection
2. Strength of fuel mixture
3. Relative velocity between the fuel injection and air turbulence pressure of residual gas
4. Engine output
Select the correct answer:
(a) 1, 2, 3 and 4
(b) 1, 2 and 3
(c) 1, 2 and 4
(d) 1, 3 and 4

Q6. At breakeven point:
(a) Sales revenue > total cost
(b) Sales revenue = total cost
(c) Sales revenue < total cost
(d) None of the above

Q7. In which of the following process, a small-diameter thick ring is expanded into a large diameter thinner ring by placing the ring between two rolls
(a) Shape rolling
(b) Tube rolling
(c) Ring rolling
(d) Continuous rolling

Q8. The instrument preferred in the measurement of highly fluctuating velocities in air flows is
(a) Pitot-static tube
(b) Propeller type anemometer
(c) Three cup anemometer
(d) Hot wire anemometer

Q9. A metal block is thrown into deep lake. As it sinks deeper in water, the buoyant force acting on it
(a) increases
(b) remains the same
(c) decreases
(d) first increases and then decreases

Q10. Match the following List-I with List-II and select the correct answer using the codes given below
List-I
A. Rigid coupling
B. Oldham’s coupling
C. Universal joint
D. Gear coupling
List-II
1. Permits greater torque capacity for a given size
2. Permits substantial angular misalignment of intersecting axes
3. Permits substantial lateral offset and little angular alignment
4. Permits almost no misalignment
Codes:
A B C D
(a) 1 2 3 4
(b) 4 2 3 1
(c) 1 3 2 4
(d) 4 3 2 1

 

SOLUTIONS

S1. Ans (a)
Sol. All of the given forces act on the connecting rod but the major force that acts on the connecting rod is the force due to gas pressure.

S2. Ans(c)
Sol. strain rosettes are generally used for measurement of longitudinal strain.
A strain gauge rosette is a term for an arrangement of two or more strain gauges that are positioned closely to measure strains along different directions of the component under evaluation. Single strain gauges can only measure strain effectively in one direction, so the use of multiple strain gauges enables more measurements to be taken, providing a more precise evaluation of strain on the surface being measured.

S3. Ans (b)
Sol. Stone crushers, embossing presses and switches works on toggle mechanism. Mechanical advantage of toggle mechanism is infinite or very large.

S4. Ans (b)
Sol. Pantograph utilizes double lever mechanism, Hand pump utilizes single slider crank chain, Scotch-yoke mechanism is an inversion of double slider crank chain and Tchebicheff mechanism is an approximate straight-line motion mechanism.

S5. Ans (a)
Sol. Following factors affects the delay period in CI engine
1. Temperature and pressure in cylinder
2. Engine output
3. Relative velocity of fuel injection and air turbulence
4. Strength of fuel mixture
5. Compression ratio

S6. Ans(b)
Sol. Breakeven point- The breakeven point is the level of production at which the costs of production equal the revenues for a product. At breakeven point, profit will be zero even there is no loss.
Which means sales revenue is equal to total cost.
Sales revenue = total cost

S7. Ans.(c)
Sol. Ring rolling is an operation of metal forming in which a small diameter, thick ring is
converted into large diameter, thinner ring by placing the ring between two rolls.

S8. Ans (d)
Sol. Hot wire anemometer is used for the measurement of highly fluctuating velocities in air. This can be done by measuring the heat loss of the wire which is placed in the fluid stream. The wire is heated by electrical current. The hot wire when placed in the stream of the fluid, in that case, the heat is transferred from wire to fluid, and hence the temperature of wire reduces. The resistance of wire measures the flow rate of the fluid which is the function of heat loss from the wire and change in the resistance of wire.

S9. Ans (b)
Sol. As buoyant force depends only on the displaced volume of fluid by the submerged or floating body according to Archimedes principle. So, volume displaced by the metal block will remain constant from when it sinks in the fluid till it sinks deeper, hence, the buoyant force on the metal block remains same.

S10. Ans (d)
Sol.
• Rigid coupling permits almost no misalignment.
• Oldham’s coupling permits substantial lateral offset and little angular alignment.
• Universal joint permits substantial angular misalignment of intersecting axes.
• Gear coupling permits greater torque capacity for a given size.

Quiz: Mechanical Engineering 19 May 2020

Quiz: Mechanical Engineering
Exam: ISRO Technical Assistant
Topic: Miscellaneous

Each question carries 1 mark
Negative marking: 1/3 mark
Time: 10 Minutes

Q1. A closed thermodynamic system is one in which
(a) there is no energy or mass transfer across the boundary
(b) there is no mass transfer, but energy transfer exists
(c) there is no energy transfer, but mass transfer exists
(d) both energy and mass transfer take place across the boundary, but the mass
transfer is controlled by valves

Q2. Which one of the following thermodynamic processes approximates the steaming of food in a pressure cooker?
(a) isenthalpic
(b) isobaric
(c) isochoric
(d) isothermal

Q3. Specific speed of a fluid machine
(a) refers to the speed of a machine of unit dimensions
(b) is a type-number representative of its performance
(c) is specific to the particular machine
(d) depends only upon the head under which the machine operates

Q4. The component of torque converter that allows torque multiplication is
(a) Turbine
(b) Impeller
(c) Stator
(d) Freewheel

Q5. Increase in entropy of a system represents
(a) Increase in availability of energy
(b) Increase in temperature
(c) Decrease in pressure
(d) Degradation of energy

Q6. Priming is necessary in
(a) Centrifugal pumps to lift water from a greater depth
(b) centrifugal pumps to remove air in the suction pipe and casing
(c) Hydraulic turbine to remove air in the turbine casing
(d) Hydraulic turbine to increase the speed of turbine and to generate more power

Q7. Air at 35°C DBT and 25°C dew point temperature passes through the water shower whose temperature is maintained at 20°C. What is the process involved?
(a) cooling and humidification
(b) sensible cooling
(c) cooling and dehumidification
(d) heating and humidification

Q8. Piston compression rings are made of which one of the following?
(a) Cast iron
(b) Bronze
(c) Aluminium
(d) White metal

Q9. The Klein’s method of construction for reciprocating engine mechanism
(a) is based on acceleration diagram
(b) is a simplified from of instantaneous centre method
(c) utilizes a quadrilateral similar to the diagram of mechanism for reciprocating engine
(d) enables determination of Coriolis component

Q10. In resistance welding, voltage used for heating is
(a) 1 V
(b) 10 V
(c) 100 V
(d) 500 V

Solutions

S1. Ans.(b)
Sol. A closed system consists of fixed amount of mass and no mass can cross its boundary but energy in the form of heat and work can cross the boundary.

S2. Ans.(c)
Sol. Volume of pressure cooker is always constant hence it is isochoric process.

S3. Ans (b)
Sol. Specific speed is of a fluid machine is a type number representative of its performance.
In order to compare the performance of different pumps, it is necessary to have some term which will be common to all the centrifugal pump the term ordinarily used for this purpose is the specific speed. This is a type characteristic and can be used to predict the behaviour of one pump based on tests of similar, but different sized pumps.
The specific speed is a characteristic of pumps which can be used as basis for comparison of the performance of different pump.

S4. Ans (c)
Sol. A hydraulic torque converter consists of series of fixed guide vanes which are provided between turbine runner and pump impeller. The liquid exerts a torque on the driven unit through these stationary guide vanes as it flows from pump to turbine runner.

S5. Ans (d)
Sol. Entropy is the measure of degree of Randomness. Increase in entropy of a system represents degradation of energy.

S6. Ans.(b)
Sol. filling the pump casing and the suction pipe with the liquid before it is started is known as priming. Unless the centrifugal pump is primed, it will not start as there is no centrifugal head impressed on the liquid. Positive displacement type reciprocating or rotary pump do not need priming because the air, if any, in the cylinder or casing is driven out by the piston or vanes.

S7. Ans.(c)
Sol. As the temperature of water shower is less than dew point temperature hence, water vapour starts condensing. Thus, process involved is cooling and dehumidification.

S8. Ans.(a)
Sol. Since grey cast iron has properties of self-lubrication and damping of small Vibration they are widely used for machine base, engine frames, drainage pipes, elevator and industrial furnace counter weights, pump housings cylinder and piston rings of IC engines, flywheel etc.

S9. Ans (c)
Sol. In Klein’s Construction, the velocity and the acceleration diagrams are made on the configuration diagram itself. The line that represents the crank in the configuration diagram also represents the velocity and acceleration of its moving end in the velocity and acceleration diagram.

S10. Ans (b)
Sol. Resistance welding processes are pressure welding processes in which heavy current is passed for short time through the area of interface of metals to be joined. These processes differ from other welding processes in the respect that no fluxes are used, and filler metal rarely used. All resistance welding operations are automatic and, therefore, all process variables are presents and maintained constant. Heat is generated in localized area which is enough to heat the metal to sufficient temperature, so that the parts can be joined with the application of pressure. Pressure is applied through the electrodes.
The process employs currents of the order of few KA, voltages range from 2 to 12 volts and times vary from few milliseconds to few seconds.

Quiz: Mechanical Engineering 18 May 2020

Quiz: Mechanical Engineering
Exam: UPSSSC JE
Topic: Miscellaneous

Each question carries 1 mark
Negative marking: 1/3 mark
Time: 10 Minutes

Q1. Which one of the following statements is correct?
(a) A machine which violates Clausius statement will violate the first law of thermodynamics
(b) A machine which violates Kelvin-Plank statement will violate the first law of thermodynamics
(c) A machine which violates the second law of thermodynamics will violate the first law of thermodynamics
(d) A machine which violates Kelvin-Plank statement will violate the Clausius statement

Q2. The conditioned air supplied to the room must have the capacity to take up
(a) Room sensible heat load only
(b) Room latent heat load only
(c) Both room sensible heat load and room latent heat load
(d) Neither room sensible heat load nor room latent heat load

Q3. Consider the following statements:
1. In model testing, the same fluid must be used in prototype and also the model
2. Models should be smaller than prototype for geometric similarity
3. Geometrically similar boundaries do not necessarily imply kinematically homogeneous flows
4. Existence of geometric similarity does not imply dynamic similarity
Which of the above statements are correct?
(a) 1 and 2 only
(b) 2 and 3 only
(c) 3 and 4 only
(d) 1 and 4 only

Q4. The discharge through a converging-diverging nozzle reaches its maximum value when the flow becomes
(a) Sonic at the exit
(b) Sonic at the throat
(c) Supersonic at the throat
(d) Subsonic at the throat

Q5. ‘Shockless entry’ of water in hydraulic turbines is of much significance from the standpoint of
(a) Hydraulic efficiency
(b) Mechanical efficiency
(c) Both hydraulic efficiency and mechanical efficiency
(d) Neither hydraulic efficiency nor mechanical efficiency

Q6. In solving a lumped parameter problem, which one of the following pair of non-dimensional numbers is used?
(a) Grashoff number and Biot number
(b) Prandtl number and Nusselt number
(c) Biot number and Fourier number
(d) Fourier number and Reynolds number

Q7. Which one of the following key types is pressed against the shaft for power transmission by friction between the key and the shaft?
(a) Feather key
(b) Square key
(c) Flat key
(d) Saddle key

Q8. The difference between member of a truss and of a beam is:
(a) The members of a truss take their loads along their length whereas a beam takes loads at right angles to its length
(b) The member of the truss takes load lateral to its length whereas the beam along the length
(c) The member of the truss can be made of C.I whereas the beam is of structural steel only
(d) The member of the truss can have a circular cross-section whereas the beam can have any cross-section

Q9. For an Oldham coupling used between two shafts, which among the following statements are correct?
I. Torsional load is transferred along shaft axis.
II. A velocity ratio of 1:2 between shafts is obtained without using gears
III. Bending load is transferred transverse to shaft axis.
IV. Rotation is transferred along shaft axis.
(a) I and II
(b) I and IV
(c) II and III
(d) II and IV

Q10. The maximum theoretical work obtainable, when a system interacts to equilibrium with a reference environment, is called
(a) Entropy
(b) Enthalpy
(c) Exergy
(d) Rothalpy

SOLUTIONS

S1. Ans(d)
Sol. A machine which violates kelvin-plank statement will violate the Clausius statement because
Kelvin-plank states that it is impossible to construct a device which operates in a cycle with single fixed temperature heat reservoir while Clausius states that it is impossible to construct a device which transfer heat from a lower temperature reservoir to a high temperature reservoir without any kind of work input. These two statements are complimentary to each other.

S2. Ans(c)
Sol. The conditioned air supplied to the room must have the capacity to take up Both room sensible heat and latent heat loads.

S3. Ans(c)
Sol. following observations can be made-
(a) Existence of geometric similarity does not imply dynamic similarity.
(b) Geometrically similar boundaries do not necessarily imply kinematically homogeneous flows.

S4. Ans(b)
Sol. The discharge through a converging-diverging nozzle reaches its maximum value when the flow becomes Sonic at the throat for which Mach number value is 1.

S5. Ans(a)
Sol. ‘Shockless entry’ of water in hydraulic turbines is of much significance from the standpoint of Hydraulic efficiency.
The hydraulic efficiency of hydraulic turbine is very much affected by shock less entry. Shock less entry in turbine ensure that the power loss in the turbine is less.

S6. Ans(c)
Sol. In solving a lumped parameter problem, pair of non-dimensional number such as Biot number and Fourier number is used.
Significance of Biot Number-
(a) Biot Number tells us whether lumped heat analysis is applicable or not.
If Bi<0.1 only then lumped heat analysis is applicable
(b) As it is the ratio of conductive resistance to convective resistance, it signifies low conductive resistance and large convective resistance.
Significance of Fourier Number-
(a) It signifies degree of penetration of heating or cooling effect.
(b) It is a measure of heat conducted through a body relative to heat stored.

S7. Ans(d)
Sol. saddle key is used for power transmission by friction between the key and the shaft.
(a) saddle key – saddle key is the key which is fit into the keyway of the hub only and no keyway in the shaft. It is likely to slip round under the shaft under load.
(b) feather key – feather key is the parallel key which is faster to one part (hub/shaft) with the help of the screws.
(c) square key – square key is the key having square cross-section.
(d) flat key – flat key is a taper key having provision in the hub only and will be floated on the shaft and the shaft is hold by mean of friction.

S8. Ans(b)
Sol. The difference between member of a truss and of a beam is the member of the truss takes load lateral to its length whereas the beam along the length.
Truss- A truss is a structure that consists of members organised into connected triangles so that the overall assembly behaves as a single object. Trusses are most commonly used in bridges, roofs and towers. A truss is made up of a web of triangles joined together to enable the even distribution of weight and the handling of changing tension and compression without bending or shearing. The triangle is geometrically stable when compared to a four (or more) -sided shape which requires that the corner joints are fixed to prevent shearing.
Beam- A beam is a structural element that primarily resists loads applied laterally to the beam’s axis. Its mode of deflection is primarily by bending. The loads applied to the beam result in reaction forces at the beam’s support points. The total effect of all the forces acting on the beam is to produce shear forces and bending moments within the beam, that in turn induce internal stresses, strains and deflections of the beam. Beams are characterized by their manner of support, profile (shape of cross-section), equilibrium conditions, length, and their material.

S9. Ans(b)
Sol. Oldham’s coupling is used to transmit power between two shafts having small angular misalignment. There is no bending load or reduction/increase of speed criterion. Hence only I and IV statements are correct.

S10. Ans(c)
Sol. As per the definition of the Exergy (or) Available Energy, we know that the maximum portion of energy which could be converted into useful work by ideal processes which reduce the system to dead state is known as Exergy.

Quiz: Mechanical Engineering 1 May 2020

Quiz: Mechanical Engineering
Exam: NLC-GET
Topic: Miscellaneous

Each question carries 1 mark
Negative marking: 1/4 mark
Time: 10 Minutes
Q1. A system will be thermodynamic equilibrium only if it is in __________.
A. Thermal equilibrium
B. Mechanical equilibrium
C. Chemical equilibrium
(a) only A
(b) only B
(c) only C
(d) A, B and C
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10

Q2. Davis steering gear consists of __________.
(a) Sliding pairs
(b) Turning pairs
(c) Rolling pairs
(d) Higher pairs
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10

Q3. Moisture in a refrigerant system is removed by ________.
A. Driers
B. Filter driers
C. Desiccants
(a) only A
(b) only B
(c) only C
(d) A, B and c
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10

Q4. Lithium bromide in vapour absorption refrigeration system is used as ___________.
(a) refrigerant
(b) cooling substance
(c) auxiliary refrigerant
(d) absorbent
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10

Q5. During sensible cooling process __________.
(a) specific humidity remains constant
(b) specific humidity increases
(c) specific humidity decreases
(d) specific humidity is unpredictable
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10

Q6. One dimensional flow is _______.
(a) restricted to flow in a straight line
(b) uniform flow
(c) one which neglects changes in a transverse direction
(d) the most general flow
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10

Q7. Alloy steel as compared to carbon steel is more ____________.
A. tough
B. brittle
C. fatigue resistance
(a) only A
(b) only B
(c) only C
(d) None of these
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10

Q8. The non-traditional machining process that essentially requires vacuum is
(a) electron beam machining
(b) electro chemical machining
(c) electro chemical discharge machining
(d) electro discharge machining
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10

Q9. The part of a gating system which regulates the rate of pouring of molten metal is
(a) pouring basin
(b) runner
(c) choke
(d) ingate
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10

Q10. Couette flow is characterized by
(a) steady. incompressible, laminar flow through a straight circular pipe
(b) filly developed turbulent flow through a straight circular pipe
(c) steady, incompressible, laminar flow between two fixed parallel plates
(d) steady. incompressible, laminar flow between one fixed plate and the other moving with a constant velocity
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10

Solutions

S1. Ans(d)
Sol. A system is said to be in equilibrium when system has achieved all the three equilibrium as given below Thermal equilibrium, Mechanical equilibrium, Chemical equilibrium.

S2. Ans(a)
Sol. Davis steering system or Davis steering gear is the most used power steering system. Almost all cars are installed with the power steering system. This is a type of side pivot steering mechanism which has only sliding pair system.

S3. Ans(b)
Sol. To avoid entry of moisture content in compressor moisture in a refrigerant system is removed by filter driers.

S4. Ans(d)
Sol. Lithium bromide in vapour absorption refrigeration system is used as absorbent.

S5. Ans(a)
Sol. Sensible heat is the energy in the air due to the temperature of the air and the latent heat is the energy in the air due to the moisture of the air. So, for sensible cooling no change in moisture content hence specific humidity remain constant.

S6. Ans(c)
Sol. Term one dimensional, two dimensional and three dimensional flow refers to the number of space coordinated required to describe a flow.

S7. Ans(d)
Sol. Alloy steel is a type of steel that has presence of certain other elements apart from iron and carbon. Commonly added elements in alloy steel are manganese, silicon, boron, chromium, vanadium and nickel. The quantity of these metals in alloy steel is primarily dependent upon the use of such steel. Normally alloy steel is made to get desired physical characteristics in the steel. Carbon steel is also known as plain steel and is an alloy of steel where carbon is the main constituent and no minimum percentage of other alloying elements is mentioned. Carbon steel is not stainless steel as it is classified under alloy steels. As the name implies, carbon content is increased in the steel making it harder and stronger through application of heat treatments. However, addition of carbon makes the steel less ductile. The weldability of carbon steel is low and higher carbon content also lowers the melting point of the alloy.

S8. Ans(a)
Sol. In electron- beam machining, vacuum conditions are required for material removal, because electrons can ionise the presence air inside the chamber. So, we created the vacuum inside the chamber.

S9. Ans(c)
Sol. Rate of poring molten metal is regulated by choke. As, the choke area is the minimum area of the gating system, which decide the gating will be pressurized and unpressurised. Hence, choke is the part which regulates the rate of pouring.

S10. Ans(d)
Sol. Couette flow is the laminar flow of a viscous fluid in the space between two parallel plates, one of which is moving relative to the other.

Quiz: Mechanical Engineering 24 April 2020

Quiz: Mechanical Engineering
Exam: NLC-GET
Topic: Miscellaneous

Each question carries 1 mark
Negative marking: 1/4 mark
Time: 10 Minutes
Q1. If the discharge of a centrifugal pump is throttled then its suction lift

(a)Decreases
(b) First increases and then decreases
(c) Remains unchanged
(d) Increases

Q2. If two objects are weighed in water and both of them lose the same weight, then the two objects must have identical

(a) Specific gravities
(b) Weights in air
(c) Densities
(d) Volumes

Q3. Which of the following regions of the electromagnetic spectrum would be used to determine the structure of crystalline solids?

(a) Microwave
(b) Infrared
(c) X-ray
(d) Visible

Q4. Precipitation hardening is applicable for

(a) Pure aluminium
(b) Low carbon steel
(c) Non- metal
(d) Aluminium- Copper alloy

Q5. Dislocations in material are

(a) Point defect
(b) Surface defect
(c) Planer defect
(d) Line defect

Q6. In the arc welding, penetration is minimum for

(a) DCSP
(b) DCRP
(c) AC
(d) DCEN

Q7. Two beams of equal cross-sectional area are subjected to equal bending moment. If one beam has square section and the other has circular section then.

(a) Both the beam will be equally strong
(b) Square section beam will be stronger
(c) Circular section beam will be stronger
(d) Depends on loading condition

Q8. To ensure self-locking in screw jack, it is essential that helix angle is

(a) Larger than friction angle
(b) None of these
(c) Equal to friction angle
(d) Smaller than friction angle

Q9. For a given heat flow and for the same thickness, the temperature drop across the material will be maximum for

(a) copper
(b) steel
(c) glass -wool
(d) refractory brick

Q10. A positive value of joule- Thompson coefficient of a fluid means

(a) Temperature drops during throttling
(b) Temperature remains constant during throttling
(c) Temperature rises during throttling
(d) None of these

SOLUTIONS

S1. Ans (d)
Sol. Due to decrease in flowrate velocity head loss as well as frictional loss decreases, by applying the Bernoulli’s equation, pump static suction pressure will increase.
As a result of this, NPSH will increases.

S2. Ans (d)
Sol. Buoyancy depends upon water volume displaced by body.
If volumes will be the same then lose in the weight of the body will also be the same.

S3. Ans (c)
Sol. X-ray diffraction method is used for the study of the material internal structure.

S4. Ans (d)
Sol. Precipitation hardening, also called age or particle hardening, is a heat treatment process that helps make metals stronger. The process does this by producing uniformly dispersed particles within a metal’s grain structure that help hinder motion and thereby strengthen it.

S5. Ans (d)
Sol. A dislocation is a linear crystallographic defect or irregularity within a crystal structure which contains an abrupt change in the arrangement of atoms.

S6. Ans (b)
Sol. In DC reverse polarity, electrons are transferred from plate to the electrode, so more heat (2/3 of total heat) generation takes place at electrode.

S7. Ans (c)
Sol. From same cross section area circular section beam has more section modulus than that of square section.

S8. Ans (d)
Sol. Helix angle should be smaller than friction angle to provide self-locking in screw jack.

S9. Ans(a)
Sol. Copper having the highest thermal conductivity along all the given options. So, it will give highest temp drop for same thickness.

S10. Ans(a)
Sol. Pressure is always decreasing in throttling process for positive Joule-Thompson coefficient temperature will drop.

QUIZ:Mechanical Engineering 18 April 2020

Quiz: Mechanical Engineering
Exam: UPPSC AE
Topic: Metal forming

Each question carries 1 mark
Negative marking: 1/4 mark
Time: 10 Minutes

Q1. Anisotropy in rolled component is caused by

(a)Change in dimensions

(b)Scale formation

(c)Closure of defects

(d)Grain orientation

L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10

Q2. The effect of friction on the rolling mill is

(a)Always bad since it retards exit of reduced metal

(b)Always good since it drags metal in to the gap between the rolls

(c)Advantageous before the neutral point

(d)Advantageous after the neutral point

L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10

Q3. Which one of the following is an advantage of forging?

(a)Good surface finish

(b)Low tooling cost

(c)Close tolerances

(d)Improved physical properties

L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10

Q4. Consider the following statements:

1.Forging reduces the grain size of the metal, which results in a decrease in strength and toughness.

2.Forged components can be provided with thin sections, without reducing the strength.

Which of the statements given above is/are correct?

(a)Only1

(b)Only2

(c)Both1and2

(d)Neither1nor2

L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10

Q5. Which of the following processes induce more stress in the metal?

(a)Hot rolling

(b)Forging

(c)Swaging

(d)Turning

L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10

Q6. In hot die forging, thin layer of material all around the forging is

(a)Gutter space, which fills up hot gases

(b) Flash the width of it is an indicator of the pressure developed in the cavity

(c) Coining, which indicates the quality of the forging

(d) Cavity which is filled with hot impurities in the material

L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10

Q7. Which one of the following manufacturing processes requires the provision of ‘gutters’?

(a) Closed die forging

(b) Centrifugal casting

(c) Investment casting

(d) Impact extrusion

L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10

Q8. In the forging operation, fullering is done to

(a)Draw out the material

(b)Bend the material

(c)Upset the material

(d) extruding the material

L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10

Q9. Extrusion process can effectively reduce the cost of product through

(a)Material saving

(b)process time saving

(c)Saving in tooling cost

(d)saving in administrative cost

L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10

Q10. Which one of the following lubricants is most suitable for drawing mild steel wires?

(a)Sodium stearate

(b)Water

(c)Lime water

(d)Kerosene

L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10

 

SOLUTIONS

S1. Ans(d)

Sol. Anisotropy in rolled component is caused by directional grain deformation.

S2. Ans(c)

Sol.

S3. Ans(d)

Sol. forging gives the directional grain formation which causes improve the physical properties of material.

S4. Ans(b)

Sol. forging increases the strength and toughness of material.

S5. Ans(b)

Sol.

S6. Ans(b)

Sol. In hot die forging, thin layer of material all around the forging is flash the width of it is an indicator of the pressure developed in the cavity.

S7. Ans(a)

Sol. closed die forging requires the provision of gutters to provide space for excess material and ensures complete closure of die and defect free forged part.

S8. Ans(a)

Sol. In the forging operation, fullering is done to Draw out the material.

S9. Ans(c)

Sol.  Advantages of extrusions-

(1) Material saving

(2) process time saving

(3) Saving in tooling cost

(4) saving in administrative cost

But only a die change can change the product is the most effective advantage among these given options

So, saving in tooling cost is most appropriate option.

S10. Ans(c)

Sol. Lime water is the most suitable lubricant for drawing mild steel wires.

Quiz: Mechanical Engineering 15 April 2020

Quiz: Mechanical Engineering
Exam: USSSC JE
Topic: Miscellaneous

Each question carries 1 mark
Negative marking: 1/4 mark
Time: 10 Minutes

Q1. The normal stress is the same in all directions at a point in a fluid only when
(a) the fluid is frictional
(b) the fluid is frictionless and incompressible
(c) the fluid has zero viscosity and is at rest
(d) one fluid layer has no motion relative to an adjacent layer
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10
Q2. In a section undergoing pure bending, the neutral surface is subjected to
(a) compressive strain
(b) tensile strain
(c) zero strain
(d) None of these
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10
Q3. The unit of temperature in S.I. units is
(a) Centigrade
(b) Celsius
(c) Fahrenheit
(d) Kelvin
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10
Q4. In a diesel engine, the fuel is ignited by
(a) spark
(b) injected fuel
(c) heat resulting from compressing air that is supplied for combustion
(d) ignitor
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10
Q5. The locus of the moment of inertia about inclined axis to the principal axis is
(a) straight line
(b) parabola
(c) circle
(d) ellipse
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10
Q6. Which material is used for bushes in the bushed pin type of flexible coupling/
(a) Gun metal
(b) Plastic
(c) Rubber
(d) Aluminum
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10
Q7. Which of the following cycles uses air as the refrigerant?
(a) Ericsson
(b) Stirling
(c) Carnot
(d) Bell-Coleman
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10
Q8. Resilience of a material is considered when it is subjected to
(a) fatigue
(b) Creep
(c) shock loading
(d) resonant condition
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10
Q9. In a kinematic chain, a tertiary joint is equivalent to:
(a) two binary joints
(b) three binary joints
(c) one binary joint
(d) four binary joints
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10
Q10. The thread used for transmission of power is
(a) Square thread
(b) Buttress thread
(c) Acme thread
(d) British association thread
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10

SOLUTIONS:-

S1. Ans (d)
Sol.

S2. Ans.(c)
Sol. For a section undergoing pure bending. The neutral surface is subjected to zero strain.

S3. Ans(d)
Sol. There are 7 base units in S.I. system
Mass = Kilogram (kg)
Temperature = Kelvin (k)
Time = Second (s)
Distance = Meter (m)
Electric current = Ampere (A)
Amount of substance = Mole (mol)
Luminous intensity = Candela (cd)

S4. Ans(c)
Sol.

S5. Ans(d)
Sol. The locus of moment of Inertia about principal axis is ellipse.

S6. Ans(c)
Sol. Rubber is used for bushes in bushed pin type flexible coupling due to flexibility of rubber.

S7. Ans(d)
Sol. The Air Refrigeration System works on Bell – Coleman Cycle.

S8. Ans(c)
Sol. Resilience is the ability of material to absorb energy with in the elastic limit & release by unloading.

S9. Ans.(a)
Sol.
1 Tertiary joint =2 binary joints

S10. Ans.(a)
Sol. for power transmission square threads are used as it has high efficiency. Applications of square threads are screw Jack, power transmission mechanism etc.

Quiz: Mechanical engineering 10 April 2020

Quiz: Mechanical Engineering
Exam: UPPSC AE
Topic: Miscellaneous

Each question carries 1 mark
Negative marking: 1/4 mark
Time: 10 Minutes
Q1. Which of the following statements regarding thin and thick cylinders, subjected to internal pressure only, is/are correct?
1. A cylinder is considered thin when the ratio of its inner diameter to the wall thickness is less than 15.
2. In thick cylinders, tangential stress has highest magnitude at the inner surface of the cylinder and gradually decreases towards the outer surface.
(a) 1 only
(b) 2 only
(c) Both 1 and 2
(d) Neither 1 nor 2
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10
Q2. Which one of the following statements regarding screw dislocation is correct?
(a) It lies parallel to its Burgers vector.
(b) It moves in the direction parallel to its Burgers vector.
(c) It initially requires very less force to move
(d) It moves very fast as compared to edge dislocation
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10
Q3. In the study of phase diagrams, the rule which helps to calculate the relative proportions of liquid and solid material present in the mixture at any given temperature is known as
(a) Hume-Rothery rule
(b) Lever rule
(c) Gibb’s phase rule
(d) Empirical rule
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10
Q4. The addition of alloying element nickel to cast iron will primarily improve
(a) Wear resistance
(b) Toughness
(c) Carbide formation
(d) Machinability
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10
Q5. The maximum energy which can be stored in a body up to the elastic limit is called
(a) Proof resilience
(b) Modulus of resilience
(c) Impact toughness
(d) Endurance strength
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10
Q6. In which one of the following tooth profiles, does the pressure angle remain constant throughout the engagement of teeth?
(a) Cycloidal
(b) Involute
(c) Conjugate
(d) Epicycloid
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10
Q7. If the axes of the first and last wheels of a compound gear coincide, it is called
(a) Simple gear train
(b) Compound gear train
(c) Epicyclic gear train
(d) Reverted gear train
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10
Q8. Coaxing is a process of_____.
(a) Improving the fatigue properties, attained by under-stressing and then raising the stress in small increments
(b) Decreasing the hardness by full annealing
(c) Increasing the uniaxial tensile strength by heating above recrystallization temperature and quenching in oil media
(d) Maintaining the ductility of the material by chemical treatment
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10
Q9. For the prediction of ductile yielding, the theory of failure utilized is
(a) Maximum strain energy theory
(b) Distortion energy theory
(c) Maximum normal strain theory
(d) Mohr theory
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10
Q10. Which of the following applications regarding Navier-Stokes equations are correct?
1. Laminar unidirectional flow between stationary parallel plates.
2. Laminar unidirectional flow between parallel plates having no relative motion.
3. Laminar flow in circuit pipes.
4. Laminar flow between concentric rotating cylinders.
(a) 1, 2 and 3 only
(b) 1, 3 and 4 only
(c) 1, 2 and 4 only
(d) 2, 3 and 4 only
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10

SOLUTIONS
S1. Ans(d)
Sol.
S2. Ans(a)
Sol. In a screw dislocation, the dislocation lies in a direction parallel to Burger’s vector.
S3. Ans(b)
Sol. Lever rule is used to study the relative proportion of two phases present in an alloy, at any given temperature.
S4. Ans(b)
Sol. Nickel promotes formation of small discontinuous carbides and enhance toughness
S5. Ans(a)
Sol. The maximum energy which can be stored in a body upto elastic limit, is called proof resilience.
S6. Ans(b)
Sol. In involute profile tooth, because of the involute property to be satisfied, pressure angle does not change with point of contact position.
S7. Ans(d)
Sol. Reverted gear train is that compound gear train, which is used to connect co-axial shafts
S8. Ans(a)
Sol.
S9. Ans(b)
Sol. For ductile material MDET result is best.
S10. Ans(a)
Sol.

Quiz..Mechanical Engineering 4th april 2020

Quiz: Mechanical Engineering
Exam: UPPSC AE
Topic: Miscellaneous

Each question carries 1 mark
Negative marking: 1/4 mark
Time: 10 Minutes
Q1. An ideal cycle based on the concept of combination of two heat transfer processes, one at constant volume and the other at constant pressure, is called
(a) Otto cycle
(b) Dual cycle
(c) Diesel cycle
(d) Carnot cycle
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10

Q2. A fictitious pressure that, if it acted on the piston during the entire power stroke, would produce the same amount of Net-work as that produced during the actual cycle is called
(a) Quasi equivalent pressure
(b) Mean equivalent pressure
(c) Mean effective pressure
(d) Quasi static pressure
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10

Q3. Which of the following characteristics regarding fluid kinematics is/are correct?
1. Streamline represents an imaginary curve in the flow field so that the tangent to the curve at any point represents the direction of instantaneous velocity at that point.
2. Path lines, streamlines and streak lines are identical in steady flow.
(a) 1 only
(b) 2 only
(c) Both 1 and 2
(d) Neither 1 nor 2
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10

Q4. Which of the following applications regarding Navier-Stokes equations are correct?
1. Laminar unidirectional flow between stationary parallel plates.
2. Laminar unidirectional flow between parallel plates having no relative motion.
3. Laminar flow in circuit pipes.
4. Laminar flow between concentric rotating cylinders.
(a) 1, 2 and 3 only
(b) 1, 3 and 4 only
(c) 1, 2 and 4 only
(d) 2, 3 and 4 only
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10

Q5. During crushing or bearing failure of riveted joints.
(a) The holes in the plates become oval shaped and joints become loose
(b) There is tearing of the plate at an edge
(c) The plates will crack in radial directions and joints fail
(d) The rivet heads will shear out by applied stress
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10

Q6. For the prediction of ductile yielding, the theory of failure utilized is
(a) Maximum strain energy theory
(b) Distortion energy theory
(c) Maximum normal strain theory
(d) Mohr theory
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10

Q7. Coaxing is a process of_____.
(a) Improving the fatigue properties, attained by under-stressing and then raising the stress in small increments
(b) Decreasing the hardness by full annealing
(c) Increasing the uniaxial tensile strength by heating above recrystallization temperature and quenching in oil media
(d) Maintaining the ductility of the material by chemical treatment
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10

Q8. If the axes of the first and last wheels of a compound gear coincide, it is called
(a) Simple gear train
(b) Compound gear train
(c) Epicyclic gear train
(d) Reverted gear train
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10

Q9. In which one of the following tooth profiles, does the pressure angle remain constant throughout the engagement of teeth?
(a) Cycloidal
(b) Involute
(c) Conjugate
(d) Epicycloid
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10

Q10. The maximum energy which can be stored in a body up to the elastic limit is called
(a) Proof resilience
(b) Modulus of resilience
(c) Impact toughness
(d) Endurance strength
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10

SOLUTIONS
S1. Ans(b)
Sol. Dual cycle is the cycle in which heat addition will take place not only at constant volume but at constant pressure also.

S2. Ans(c)
Sol. As we know that the fictitious pressure is known as by the name of MEAN EFFECTIVE PRRESSURE.
WORK DONE = (MEAN EFFECTIVE PRESSURE) x (SWEPT VOLUME)
S3. Ans(c)
Sol.

S4. Ans(a)
Sol.

S5. Ans(a)
Sol. Crushing strength of plate/rivet crushing failure of the plate/rivet. This type of failure occurs when the compressive stress between the shank of the rivet and the plate exceeds the yield stress in compression. The failure results in elongating the rivet hole in the plate and loosening of the joint.

S6. Ans(b)
Sol. For ductile material MDET result is best.

S7. Ans(a)
Sol.

S8. Ans(d)
Sol. Reverted gear train is that compound gear train, which is used to connect co-axial shafts

S9. Ans(b)
Sol. In involute profile tooth, because of the involute property to be satisfied, pressure angle does not change with point of contact position.

S10. Ans(a)
Sol. The maximum energy which can be stored in a body upto elastic limit, is called proof resilience

Quiz: Mechanical Engineering 3 April 2020 

Quiz: Mechanical Engineering
Exam: NLC GET
Topic: Miscellaneous

Each question carries 1 mark
Negative marking: 1/4 mark
Time: 10 Minutes
Q1. Working cycle in case of four stroke engine is completed in following number of revolutions of crankshaft?
(a) 1/2
(b) 1
(c) 2
(d) 4
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10
Q2. The crank shaft turning in a journal bearing forms a
(a)turning pair
(b)sliding pair
(c)rolling pair
(d)helical pair
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10
Q3. A standard ice point temperature corresponds to the temperature of
(a) water at 0°C
(b) ice at – 4°C
(c) mixture of ice, water and vapour under equilibrium conditions under NTP conditions
(d) mixture of ice and water under equilibrium conditions.
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10
Q4. A column pinned at both the ends has length L and flexural rigidity EI can carry a
critical load of:
(a) (4π^2 EI)/L^2
(b) (2π^2 EI)/L^2
(c) (π^2 EI)/L^2
(d) (π^2 EI)/〖4L〗^2
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10
Q5. In a four-degree freedom system the number of eigen values is………………
(a) 0
(b) 3
(c) 4
(d) 2
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10
Q6. What strength of the material is to be considered for design of a ductile component
under cyclic load?
(a) Ultimate strength
(b) Yield strength
(c) Endurance strength
(d) fracture strength
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10
Q7. According to Dalton’s law, the total pressure of the mixture of gases is equal to
a) greater of partial pressure of all
(b) average of the partial pressure of all
c) sum of partial pressure of all
(d) sum of partial pressure of all divided by average molecular weight
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10
Q8. Match list-I (Material) with List – II (young’s modulus):
List – I List – II
A. Brass 1. 83-170 GPa
B. Steel 2. 96-110 GPa
C. Aluminium alloys 3. 70-79 GPa
D. Cast iron 4. 48-83 GPa
5. 190-210 GPa
Codes:
A B C D
(a) 2 5 3 1
(b) 2 3 5 4
(c) 2 3 5 1
(d) 2 5 3 4
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10
Q9. Shear span is defined as the zone where:
(a) bending moment is zero
(b) shear force is zero
(c) shear force is constant
(d) bending moment is constant
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10
Q10. The piston rod of a steam engine is usually connected by the crosshead by means of
(a) Bolted joint
(b) Cotter joint
(c) Universal joint
(d) Knuckle joint
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10

SOLUTIONS
S1. Ans (c)
Sol.
S2. Ans.(a)
Sol. shaft moves in a journal bearing moves like a turning pair

S3. Ans (d)

Sol.

S4. Ans.(c)

Sol.

Leff= L
P = (π^2 EI)/L^2

S5. Ans.(c)

Sol. D.O.F of a system are the eigen values that satisfy the characteristics equation of the system.

S6. Ans.(c)

Sol. As value of endurance strength is less than that of yield strength and in cyclic loading material can fail before yielding due to fatigue in the material.
Hence, Endurance strength is considered for the design.

S7. Ans (c)
Sol. Dalton’s law of partial pressures states that the total pressure of a mixture of gases is equal to the sum of the partial pressure of the component gases:
P_Total=P_gas1+P_gas2+P_gas3……..
S8. Ans.(a)

Sol.
Material Modules of Elasticity (GPa)
Alluminium alloys 70-79
Brass 96-110
Bronze 96-120
Cast Iron 83-170
Rubber 0.0007-0.004
Steel 190-210

S9. Ans.(c)

Sol. Shear span is the distance from the point of application of concentrated force to its respective reaction force. throughout shear span the shear force is constant.
“Shear span is defined as the zone where shear force is constant.”

S10. Ans.(b)

Sol. Cotter joint

Quiz: Mechanical Engineering 1 April 2020

Quiz: Mechanical Engineering 1 April 2020
Exam: USSSC JE
Topic: Miscellaneous

Each question carries 1 mark
Negative marking: 1/4 mark
Time: 10 Minutes

Q1. The centre of pressure for an inclined surface area
(a) Lies below the centroid of the surface
(b) Coincides with the centroid
(c) Lies above the centroid of the surface
(d) None of the above
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10
Q2. A bucket of water hangs with a spring balance. If an iron piece is suspended into water from another support without touching the sides of the bucket, the spring balance will show
(a) an increased reading
(b) a decreased reading
(c) no change in reding
(d) increased or decreased reading depending on the depth of immersion
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10
Q3. Match List-I (Measuring device) with List-II (Parameters) regarding a body partly submerged in a liquid and select the correct answer using the codes given below the lists:
List-I List-II
A. Anemometer 1. Flow rate
B. Piezometer 2. Velocity
C. Pitot tube 3. Static pressure
D. Orifice 4. Difference between static and stagnation pressure
Codes :
A B C D
(a) 1 3 4 2
(b) 1 2 3 4
(c) 2 3 4 1
(d) 2 4 3 1
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10
Q4. Priming is necessary in
(a) Centrifugal pumps to lift water from a greater depth
(b) centrifugal pumps to remove air in the suction pipe and casing
(c) Hydraulic turbine to remove air in the turbine casing
(d) Hydraulic turbine to increase the speed of turbine and to generate more power
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10
Q5. Match List-I with List-II and select the correct answer using the codes given below the lists:
List I
Work done in a polytropic process
Work done in steady flow process
Heat transfer in a reversible adiabatic process
Work done in an isentropic process
List- II
-∫▒Vdp
Zero
(p_1 V_1-p_2 V_2)/(γ-1)
4. (p_1 V_1-p_2 V_2)/(n-1)
Codes
A B C D
(a) 4 1 3 2
(b) 1 4 2 3
(c) 4 1 2 3
(d) 1 2 3 4
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10
Q6. In a heat engine operating in a cycle between a source temperature of 606°C and a sink temperature of 20°C, what will be the least rate of heat rejection per kW net output of the engine?
(a) 0.50 kW
(b) 0.667 kW
(c) 1.5 kW
(d) 0.0341 kW
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10
Q7. Match list I with list II and select the correct answer using the codes given below the lists:
List – I List – II
A. Bell Coleman refrigeration 1. Compressor
B. Vapour compression refrigeration 2. Generator
C. Absorption refrigeration 3. Flash chamber
D. Jet refrigeration 4. Expansion cylinder
codes
A B V D
(a) 1 4 3 2
(b) 4 1 3 2
(c) 1 4 2 3
(d) 4 1 2 3
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10
Q8. The knocking tendency in compression ignition engines increases with
(a) increase of coolant water temperature
(b) increase of temperature of inlet air
(c) decrease of compression ratio
(d) increase of compression ratio
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10
Q9. Dimensionless time is represented by
(a) Biot number
(b) Fourier number
(c) Euler number
(d) Graetz number
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10
Q10. In a counter flow heat exchanger, the product of specific heat and mass flow rate is same for the hot and cold fluids. If NTU is equal to 0.5 then the effectiveness of the heat exchanger is
(a) 1.0
(b) 0.5
(c) 0.33
(d) 0.2
L1Difficulty 3
QTags Mechanical
QCereator Paper Maker 10

SOLUTIONS
S1. Ans.(a)
Sol.
h=x ̅+I_G/(Ax ̅ ) sin^2 θ
x ̅ = Centre of gravity
I_G = Area moment of inertia of surface about its centroidal axis and parallel to free surface.
S2. Ans.(c)
Sol.
Since the water of bucket will exert force of buoyancy equal to the volume displaced by the iron block. Hence equal and opposite force will be exerted by iron block on water hence the reading of the spring balance will increase.
S3. Ans.(c)
Sol.
Anemometer: It is device for measuring wind speed, and it a common weather station instrument.
Orifice plate: It is a device used for measuring the volumetric flow. It uses the Bernoulli’s principle.
S4. Ans.(b)
Sol. filling the pump casing and the suction pipe with the liquid before it is started is known as priming. Unless the centrifugal pump is primed, it will not start as there is no centrifugal head impressed on the liquid. Positive displacement type reciprocating or rotary pump do not need priming because the air, if any, in the cylinder or casing is driven out by the piston or vanes.
S5. Ans.(c)
Sol.
A. Work done in a polytropic process: (p_1 V_1-p_2 V_2)/(n-1)
B. Work done in steady flow process -∫▒Vdp
C. Heat transfer in a reversible adiabatic process: zero
D. Work done is an isentropic process: (p_1 V_1-p_2 V_2)/(γ-1)
S6. Ans.(a)
Sol.

T_1=606+273=879 K
T_2=20+273=293 K
η=(T_1-T_2)/T_1
=(879-293)/879=W/Q_1 (since W = 1 kW)
0.6666=〖1/Q〗_1
Q_1=1.5 kW
Amount of heat rejected
Q_2=Q_1-W=1.5-1.0=0.5 kW
S7. Ans.(d)
Sol.
1. Bell Coleman refrigeration: Expansion cylinder
2. Vapour compression refrigeration: compressor
3. Absorption refrigeration: Generator
4. Jet Refrigeration: Flash chamber
S8. Ans.(c)
Sol.
Decrease of compression ratio will reduce temperature and increase delay period. This increases the knocking tendency in CI engine.
S9. Ans.(b)
Sol. Dimensionless time is represented by Fourier number.
Mathematically, Fourier number = (αt )/(L_C^2 )
Where
α = Thermal diffusivity
=(k/ρC)
L_C = characteristics length
t = time
S10. Ans.(c)
Sol. C=1
∴ ε=NTU/(1+NTU)
ε=0.5/1.5=1/3=0.33