Freshers Mechanical Engineers Interview Questions & Answers

51. On what factor the maximum efficiency of screw jack depends ?

Ans:  Angle of friction.

52. To be on safe side which assumption is advisable for working out (i) power lost in friction ? and (ii) power transmitted by friction ?

Ans:  Uniform pressure, uniform wear respectively.

 53. State the conditions for a rigid rotor to be dynamically balanced.

Ans:  When rotor is rotated at high speed, the vibrations in two planes should be within prescribed limits. Rotor should not be operated near its natural frequency of vibrations.

54. Why involute profile is preferred to cycloidal for gears ?

Ans:  The rack for generating involulte profile on gears has straight line profile and hence such gears can be easily cut.

55. What is the condition for correct gearing ?

Ans:  According to condition of correct gearing, the common normal to the pitch surface should cut the line joining the centres at a fixed point.

56. What is the diameter of rack for gear ?

Ans:  Infinite.

57. Define transducer ?

Ans:  Transducer is an element which converts the signal from one physical form to another without changing the information content of the signal.

 58. What are Herringbone gears and what for these are used ?

Ans:  Herringbone gears are double helical gears and used to eliminate axial thrust.

59. Whether normal pressure angle in helical gear is more or less than ordinary pressure angle ?

Ans:  Less.

60. Whether tooth error is more prominent for spur or helical gears ?

Ans:  Spur gears.

61. Show the variation of the ratio of damped frequency to undamped frequency against damping ratio in case of a damped oscillator ?

Ans:  As damping ratio increases, the ratio of damped to undamped frequency decreases nearly exponentially.

62. A simple gear train has three gear wheels of 25,  and 50 teeth respectively. The speed ratio of third gear to first gear and direction are … ?

Ans:  Half and same direction.

63. The axes of first and last gear in a reverted gear train are … ?

Ans:  Coaxial.

64. Which gear train is used to connect hour hand in clock mechanism to minute hand?

Ans:  Reverted gear train.

65. If there are even number of idlers between driver and driven gears in a simple gear train, then direction of driver and driven gears will be … ?

Ans:  Opposite.

66. What for pycnometer is used ?

Ans:  Pycnometer is used to measure specific gravity of the liquid.

67. How helical gears are capable of transmitting heavy load at high speed compared to spur gears ?

Ans:  Helical gears have smooth engagement and two pairs of teeth are always in contact.

68. Which type of bearing is most suitable for helical gears ?

Ans:  Deep groove ball bearing.

69. What is the name given to bevel gears used for connecting non-intersecting shafts ?

Ans:  Hypoid gears.

70. Out of spur, bevel, helical, mitre, herringbone, hypoid, zerol gears, in which case the interchangeability is possible ?

Ans:  Spur gears.

 71. Why worm gear drive is used for hoists ?

Ans:  Because it is self locking.

72. What is the material used for worm gear pair ?

Ans:  Bronze.

73. In which type of gear pair heat dissipation is important criterion ?

Ans:  Worm gear.

74. A gear train in which axes of gears have motion is called … ?

Ans:  Epicyclic gear train.

75. If a rigid body is to be replaced by two concentrated masses rigidly connected together then what are the essential conditions for two systems to be kinetically equivalent ?

Ans:  (i)   Mass of two masses should be same as the mass of rigid body.
(ii)  Centre of gravity of two mass system should coincide with the centre of gravity of rigid body.
(iii) Mass moment of inertia of the two mass system and the rigid body about centre of gravity should be equal.