# Police Constable Consider Question 2020 | Police Constable Answer Key

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The Maharashtra Police Headquarters relocated in 1896, which was known as the home of the Royal Alfred Sailors. Construction of the building began in early 1872 and ended in 1876 after four years, Police Constable Consider Question. As its name suggests, it was built to accommodate other officers. And 100 suture. However, the building was actually conceived as a visit to the Duke of Edinburgh in 1870. The Duke laid the foundation stone during his journey, Police Constable Consider Question.

## Police Constable Consider Question 2020 :

1. Consider the following statements pertaining to stability of floating bodies :

• A floating body will be stable when the centre of gravity is above the centre of buoyancy.
• The positions of metacentric corresponding to different axes of rotation are generally different for the same floating object.

Which of the above statements are correct?

• a) 1, 2 and 3
• b) 1 and 2 only
• c) 1 and 3 only
• d) 2 and 3 only

2. Water is coming out from a tap and falls vertically downwards. At the tap opening, the stream diameter is 20 mm with uniform velocity of 2 m/s. Assuming steady inviscid flow, constant pressure atmosphere everywhere, nad neglecting curvature and surface tension effects, the diameter of the stream 0.5 m below the tap opening is nearly

• a) 11.7 mm
• b) 14.6 mm
• c) 17.5 mm
• d) 20.4 mm

3. Consider the following statements :

• At low Reynolds numbers of any flow, viscous forces dominate over inertial forces.
• Transition from laminar to turbulent flow occurs over a range of Reynolds numbers depending on the surface presented to the flow.

Which of the above statements is/are correct ?

• a) 1 only
• b) 2 only
• c) Both 1 and 2
• d) Neither 1 nor 2

4. The centre-line velocity in a pipe flow is 2 m/s. What is the average flow velocity in the pipe if the Reynolds number of the flow is 800?

• a) 2 m/s
• b) 1.5 m/s
• c) 1 m/s
• d) 0.5 m/s

5. During a constant pressure pressure expansion of a gas, 33.3% heat is converted into work while the temperature rises by 20 K. The specific heat of the gas at constant pressure as a proportion of work, W is

• a) 8%
• b) 10%
• c) 12%
• d) 15%

### Police Constable Consider Question :

6. A reversible heat engine rejects 80% of the heat supplied during a cycle of operation. If the engine is reversed and operates as a refrigerator, then its coefficient of performance shall be

• a) 6
• b) 5
• c) 4
• d) 3

7. For the same efficiency of the Brayton cycle and the Carnot cycle working between temperature limits of T max and Tmin, the power contribution of the Brayton cycle will be

• a) zero
• b) maximum
• c) minimum
• d) 50% of the Carnot cycle

8. A heat engine working on the Carnot cycle receives heat at the rate of 50 kW from a source at 1300 K and rejects it to a sink at 400 K. The heat rejected is

• a) 20.3 kW
• b) 15.4 kW
• c) 12.4 kW
• d) 10.8 kW

9. Knocking in a spark ignition engine can be reduced by

• retarding the spark
• supercharging
• increasing the engine speed
• using a fuel of long straight chain structure

Select the correct answer using the code given below.

• a) 1 and 4
• b) 1 and 3
• c) 2 and 3
• d) 2 and 4

#### Police Constable Consider Question :

10. A 4-cylinder diesel engine running at 1200 r.p.m. developed 18.6 kW. The average torque when one cylinder was cut out was 105 N m. If the calorific value of the engine used 0.34 kg of diesel/kW hr, the indicated thermal efficiency was nearly

• a) 29%
• b) 26%
• c) 31%
• d) 23%

11. In a morse test on a 2-cylinder, 2-stroke SI engine, the brake power is 9 kW and the BHP of individual cylinders with spark cutoff are 4.25 kW and 3.75 kW, respectively. The mechanical efficiency of the engine is

• a) 90%
• b) 80%
• c) 52.5%
• d) 45.5%

12. Consider the following statements for refrigeration and air-conditioning :

• In a refrigerating machine, the heat exchanger that absorbs heat is connected to a conditioned space.
• A refrigerating cycle operating reversibly between two heat reservoirs has the highest coefficient of performance.
• The lower the refrigeration required and the higher the temperature of heat rejection to the surroundings, the larger the power consumption.

Which of the above statements are correct?

• a) 1 and 2 only
• b) 1 and 3 only
• c) 2 and 3 only
• d) 1, 2 and 3

13. Consider the following statements : The volumetric efficiency of a reciprocating compressor can be improved by

• decreasing the clearance volume
• cooling the intake air
• heating the intake air

Which of the above statements is/are correct?

• a) 2 only
• b) 3 only
• c) 1 and 2
• d) 1 and 3
##### Police Constable Consider Question :

14. Consider the following statements : The presence of air inside condensers

• remains as a non-condensable gas
• reduces the condensing coefficient
• tends to cling to the surface
• introduce large thermal resistance

Which of the above statements are correct ?

• a) 1, 2, 3 and 4
• b) 1, 2 and 3 only
• c) 3 and 4 only
• d) 1, 2 and 4 only

15. Consider the following statements in respect of a vapour-absorption refrigeration cycle :

• The absorption refrigeration cycle is generally used when waste heat is available from an existing source or when free energy like solar energy is to be used.
• There are no moving parts in the absorption refrigeration plant except a small liquid pump.
• The value of the coefficient of performance is nearly the same in both vapour-absorption and vapour-compression refrigeration plants.

Which of the above statements are correct?

• a) 1, 2 and 3
• b) 1 and 2 only
• c) 1 and 3 only
• d) 2 and 3 only
##### Police Constable Consider Question :

16. Consider the following statements in respect of an evaporative cooling process

• The wet-bulb temperature remains constant.
• The dew-point temperature remains constant.
• The enthalpy remains constant.

Which of the above statements are correct ?

• a) 1, 2 and 3
• b) 1 and 2 only
• c) 2 and 3 only
• d) 1 and 3 only

17. Which of the following statements are correct?

• The specific speed of a turbine is the speed at which a homologous turbine develops 1 mhp under unit head at its maximum efficiency.
• The specific speed is a dimensionless parameter used for the selection
• The function of guide vanes in reaction turbines is to minimize shock at entry of the fluid onto the runner blades.

Select the correct answer using the code given below.

• a) 1, 2 and 3
• b) 2 and 3 only
• c) 1 and 2 only
• d) 1 and 3 only

Police Constable Consider Question :

18. Consider the following statements in respect of ideal and practical gas turbine cycles :

• In the ideal cycle case, the cycle efficiency depends on the pressure ratio only.
• In the practical cycle case (with irreversibilities in the compression and expansion processes), the cycle efficiency depends on the maximum temperature as well as on the pressure ratio.
• the practical cycle case, at a given maximum temperature, the maximum efficiency and the maximum work done occur at a same pressure ratio.

Which of the above statements are correct?

• a) 1 and 2 only
• b) 1 and 3 only
• c) 2 and 3 only
• d) 1, 2 and 3

19. A jet of water issues from a sharp-edged vertical under a constant head of 0.51 m. At a certain point of the issuing jet, the horizontal and vertical coordinates measured from vena contracta are 0.406 m and 0.085 m, respectively. What is the value of the coefficient of velocity?

• a) 0.975
• b) 0.925
• c) 0.875
• d) 0.825

20. Consider the following statements for single-stage reciprocating compressors :

• Isothermal process is the most desirable process for compression.
• The size of clearance volume provided in the compressor has no effect on work done per kg of air delivered.
• The volumetric efficiency of the compressor decreases with increasing pressure.

Which of the above statements are correct?

• a) 1 and 2 only
• b) 1 and 3 only
• c) 2 and 3 only
• d) 1, 2 and 3
##### Police Constable Consider Question :

21. Consider the following statements in respect of regenerative Rankine cycle :

• Regeneration increases the efficiency of the cycle.
• The boiler capacity is increased for a given output.
• The capacity of the condenser is reduced.

Which of the above statements are correct?

• a) 1, 2 and 3
• b) 1 and 2 only
• c) 1 and 3 only
• d) 2 and 3 only

22. Consider the following statements in respect of (l) the temperature of the medium, (m) the refrigerant and (n) the condenser and absorption system–in a refrigeration unit:

• Temperature of the medium being cooled must be below that of the evaporator.
• Refrigerant leaves the condenser as liquid.
• Any solar thermally operated absorption system is capable only of intermittent operation.

Which of the above statements are correct?

• a) 1 and 2 only
• b) 1 and 3 only
• c) 2 and 3 only
• d) 1, 2 and 3

23. Consider the following statements:

• The efficiency of heat transfer in a condenser will improve by increase of the overall heat transfer coefficient.
• The efficiency of heat transfer in a condenser will improve by increase of the velocity of flow of water in the tube.
• The difference between the temperature of steam entering the condenser and the inlet water temperature should be maximum for maximum efficiency

Which of the above statements are correct?

• a) 1 and 2 only
• b) 1 and 3 only
• c) 2 and 3 only
• d) 1, 2 and 3
##### Police Constable Consider Question :

24. The total power developed by a three stage velocity compounded impulse steam turbine is 900 kW. The power magnitudes developed in the first and the second stage are, respectively

• a) 500 kW and 300 kW
• b) 100 kW and 300 kW
• c) 500 kW and 100 kW
• d) 100 kW and 100 kW

25. Consider the following statements in respect of natural-draft cooling towers :

• Theoretically the water can be cooled to even below the dry-bulb temperature of the induced air flow.
• Nature-draft cooling towers are 100 m or mote in height.
• The inner and outer surfaces are surfaces of revolution of a segment of a hyperbola about the vertical axis–affording improved strength rater than any thermodynamic augmentation.

Which of the above statements are correct?

• a) 1, 2 and 3
• b) 1 and 2 only
• c) 1 and 3 only
• d) 2 and 3 only
##### Police Constable Consider Question

26. Consider the following statements:

• Wind velocity at about 20 m height above the ground is taken as the rated velocity for design of wind mills.
• The total power of a wind stream is directly proportional to the cube of average velocity.
• Wind turbine operates with variable load over a narrow range between cut-in and cut-out velocities.
• Vertical wind machine operates in all wind directions, but it needs yaw adjustment.

Which of the above statements are correct?

• a) 1 and 2
• b) 1 and 4
• c) 3 and 4
• d) 2 and 3

27. Which fuel cell is suitable for spacecraft applications?

• a) Direct methanol fuel cell
• b) Proton exchange membrane fuel cell
• c) Alkaline fuel cell
• d) Phosphoric acid fuel cell
##### Police Constable Consider Question :

28. A flywheel on a motor speed up from rest to 1000 r.m.p. in 6 seconds. The number of revolutions made thereby is nearly

• a) 200
• b) 100
• c) 50
• d) 20

29. A bullet of mass 0.03 kg moving with a speed of 400 m/s penetrates 12 cm into a fixed block of wood. The average force exerted by the wood on the bullet will be exerted by the wood on the bullet will be

• a) 30 kN
• b) 20 kN
• c) 15 kN
• d) 10 kN

30. The modulus of rigidity of an elastic material is found to be 38.5% of the value of its Young’s modulus. The Poisson’s ratio u of the material is nearly

• a) 0.28
• b) 0.30
• c) 0.33
• d) 0.35
##### Police Constable Consider Question :

31. In the design of beams for a given strength, consider that the conditions of economy of use of the material would avail as follows :

• Rectangular cross-Section is more economical than square section of the same cross-sectional area of the beam.
• Circular sect6ion is more economical than square section.
• I-section is economical than a rectangular section of the same depth.

Which of the above are correct?

• a) 1, 2 and 3
• b) 1 and 2 only
• c) 2 and 3 only
• d) 1 and 3 only

32. Which one of the following statements is correct?

• a) The strain produced per unit volume is called resilience.
• b) The maximum strain produced per unit volume is called proof resilience.
• c) The least strain energy stored in a unit volume is called proof resilience.
• d) The greatest strain energy stored in a unit volume of a material without permanent deformation is called proof resilience.
###### Police Constable Consider Question :

33. A beam of rectangular section (12 cm wide x 20 cm deep) is simply supported over a span of 12 m. It is acted upon by a concentrated load of 80 kN at midspan. The maximum bending stress induced is

• a) 400 MPa
• b) 300 MPa
• c) 200 MPa
• d) 100 MPa

34. A uniform bar, simply supported at the ends, carries a concentrated load P at mid-span. If the same load be, alternatively, uniformly distributed over the full length of the bar, the maximum deflection of the bar will decrease by deflection of the bar will decrease by

• a) 25.5%
• b) 31.5%
• c) 37.5%
• d) 50.0%

35. A thin cylindrical pressure vessel and a thin spherical pressure vessel have the same mean radius, same wall thickness and are subjected to same internal pressure. The hoop stresses set up in these vessels (cylinder in relation to sphere) will be in the ratio

• a) 1 : 2
• b) 1 : 1
• c) 2 : 1
• d) 4 : 1
###### Police Constable Consider Question :

36. A boy walks up a stalled escalator in 90 seconds. When the same escalator moves, he is carried up in 60 seconds. How much time would it take him to walk up the moving escalator ?

• a) 48 seconds
• b) 36 seconds
• c) 30 seconds
• d) 24 seconds

37. On completion of heat treatment, the austenite structure would be retained if

• a) the rate of cooling is greater than the critical cooling rate
• b) the rate of cooling is less than the critical cooling rate
• c) the initiating temperature of martensite formation is above the room temperature
• d) the finishing temperature of martensite formation is below the room temperature

38. Which one of the following statements is correct?

• a) Iron-carbon and TTT diagrams are both equilibrium diagrams.
• b) Iron-carbon and TTT diagrams are both non-equilibrium diagrams.
• c) Iron-carbon diagram is an equilibrium diagram but TTT diagram is a non-equilibrium diagram.
• d) Iron-carbon diagram is a non-equilibrium diagram but TTT diagram is an equilibrium diagram.
###### Police Constable Consider Question :

39. The correct order of increasing resistivity among the following materials is

• a) nickel, doped silicon, sodium silicate, pure silica
• b) doped silicon, nickel, pure silica, sodium silicate
• c) nickel, pure silica, sodium silicate, doped silicon
• d) sodium silicate, nickel, pure silica, doped silicon

40. Consider the following statements : On heating an elastomer under tensile load. its shrinkage

• maximize the enthalpy
• maximizes the entropy
• minimizes the free energy
• avoids breaking

Which of the above statements are correct?

• a) 1 and 2
• b) 2 and 3
• c) 3 and 4
• d) 1 and 4

41. Which of the following properties will be the meaningful indicator/indicators of uniform rate of elongation of a test piece of a structural material before necking happens in the test piece?

• Ductility
• Toughness
• Hardness

Select the correct answer using the code given below.

• a) 1 only
• b) 2 only
• c) 3 only
• d) 1, 2 and 3

42. Which one of the following alloying elements increases the corrosion resistance of steel?

• b) Chromium
• c) Nickel
• d) Copper

43. Which of the following mechanisms are examples of forced closed kinematic pairs?

• Cam and roller mechanism
• Door-closing mechanism
• Slider-crank mechanism

Select the correct answer using the code given below.

• a) 1 and 2 only
• b) 1 and 3 only
• c) 2 and 3 only
• d) 1, 2 and 3
###### Police Constable Consider Question :

44. A planer mechanism has 10 links and 12 rotary joints. Using Grubler’s criterion, the number of degrees of freedom of the mechanism is

• a) 1
• b) 3
• c) 2
• d) 4

45. The number of instantaneous centres of rotation in a slider-crank quick-return mechanism is

• a) 10
• b) 8
• c) 6
• d) 4
###### Police Constable Consider Question :

46. A simple spring-mass vibrating system has a natural frequency of N. If the spring stiffness is halved and the mass doubled, then the natural frequency will be

• a) 0.5N
• b) N
• c) 2N
• d) 4N

47. A car of mass 1450 kg is constructed on a chassis supported by four springs.Each spring has a force constant of 40000 Nm. The combined mass of the two people occupying the car is 150 kg.What is the period of execution of two complete vibrations?

• a) 0.63 s
• b) 1.59 s
• c) 4.96 s
• d) 1.26 s

48. Consider the following statements :  Artefacts to prevent harmful effects resulting from vibrations of an unbalanced machine fixed on its foundation include.

• mounting the machine on springs thereby minimizing the transmission of forces
• 2. using vibration isolating materials to prevent or reduce the transmission of forces
• 3. moving the foundation so as to have only one degree of freedom towards reducing the transmission of forces

Which of the above statements are correct?

• a) 1 and 2 only
• b) 1 and 3 only
• c) 2 and 3 only
• d) 1, 2 and 3
###### Police Constable Consider Question :

49. Two heavy rotors are mounted on a single shaft. Considering each of the rotors separately, the transverse natural frequencies are 100 cycles/s and 200 cycles/s, respectively. The lower critical speed will be

• a) 12000 r.m.p.
• b) 9360 r.m.p.
• c) 8465 r.m.p.
• d) 5367 r.m.p.

50. Consider the following statements : In the case of gears of involute profiles,increase in the centre to centre distances between the mounting shafts.

• increases the pressure angle
• will not affect the law of gearing
• shortens the path of contact
• increases the contact ratio

Which of the above statements are correct?

• a) 1, 2 and 4
• b) 1, 2 and 3
• c) 1, 3 and 4
• d) 2, 3 and 4