Solved Question Paper for Foreman (Mechanical) in Ministry of Defence, Junior Scientific Officer (Mechanical) in Ministry of Defence, Assistant Executive Engineer (Mechanical), Additional Assistant Director (Safety) (Mechanical), Senior Scientific Assistant (Mechanical), Ministry of Defence & Junior Works Manager (Mechanical), Ministry of Defence conducted by UPSC

51. Balancing of industrial rotors in a balancing machine is usually done at speeds between 400 rpm and 700 rpm , because:


1. Industrial rotors have lateral critical speeds more than 5000 rpm

2. The rotor has critical speed generally less than 100 rpm

3. Speeds lower than 400 rpm do not create centrifugal forces of magnitudes measurable in this set up

4. Balanced rotors have no critical speed

Which of the above statements are correct?

(a) 1 and 4 only

(b) 1 and 3 only

(c) 2 and 3 only

(d) 2 and 4 only

Answer: (b)

52. 

(a) 300 𝑚𝑚

(b) 425 𝑚𝑚

(c) 550 𝑚𝑚

(d) 675 𝑚𝑚

Answer: (d)

53. Transmissibility is defined as

(a) Ratio of force applied to the force transmitted to the foundation

(b) Ratio of force transmitted to the foundation to the input force

(c) Sum of the forces applied and the force transmitted to the foundation

(d) Difference of force applied vis-a-vis the force transmitted to the foundation

Answer: (b)

54. Statement (I): In ordinary drop-forging with flash, die cavity is properly filled with metal.

Statement (II): Forging load increases by increasing flash thickness.

(a) Both Statement (I) and Statement (II) are individually true and Statement (II) is the correct explanation of Statement (I)

(b)Both Statement (I) and Statement (II) are individually true but Statement (II) is NOT the correct explanation of Statement (I)

(c)Statement (I) is true but Statement (II) is false

(d)Statement (I) is false but Statement (II) is true

Answer: (c)

55. 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

Answer: (d)

56. The factor of safety provided for the cotter is less than that for the spigot and socket end because

1. There is stress concentration in the cotter

2. There is no stress concentration in the cotter

3. The cotter is not as weaker as the spigot and socket end

4. The cotter has been made from materials different from that of the spigot and socket end

Which of the above statements are correct?

(a) 1 and 3 only

(b) 1 and 4 only

(c) 2 and 3 only

(d) 2 and 4 only

Answer: (c)

57. What is the preferred order of sequence for the following drives from high speed to low speed?

(a) Rack and pinion, spur gears, worm and worm wheel

(b) Worm and worm wheel, spur gears, rack and pinion

(c) Worm and worm wheel, rack and pinion, spur gears

(d) Spur gears, worm and worm wheel, rack and pinion

Answer: (d)

58. Design load factor for (i) a helical gear is smaller than that for (ii) a straight tooth spur gear because

(a) Load concentration factor may be same in both but dynamic load factor is smaller in (i)

(b) Both load concentration factor and dynamic load factor are smaller in (i)

(c) Load concentration factor is smaller even though dynamic load factor may be higher in (i)

(d) Load concentration factor is smaller in (i) even as the dynamic load factor is the same for both

Answer: (a)

59. An elevator weighing 10 𝑘N attains an upward velocity of 4 𝑚/𝑠 in 2 sec with uniform acceleration. The tension in the wire rope is nearly

(a) 6 kN

(b) 8 kN

(c) 10 kN

(d) 12 kN

Answer: (d)

60. For a single row angular contact ball bearing, the basic dynamic capacity is 55 kN and the dynamic equivalent load is 3950 N. The rated life of the bearing is:

(a) 2700 Million revolutions

(b) 2200 Million revolutions

(c) 1700 Million revolutions

(d) 1200 Million revolutions

Answer: (a)
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