SECTION-4

##### Q51. A system is said to be critically damped if the damping factor for a vibrating system is

(a) more than one
(b) equal to one
(c) less than one
(d) equal to zero.

Ans:  (b) equal to one

##### Q52. The amount of damping, necessary for a system to be critically damped, is known as

(a) damping factor
(b) magnification factor
(c) critical damping co-efficient
(d) logarithmic decrement.

Ans:  (c) critical damping co-efficient

##### Q53. The ratio of the actual damping co-efficient to the critical damping co-efficient is known as

(a) damping factor
(b) magnification factor
(c) critical damping co-efficient
(d) logarithmic decrement.

Ans:  (a) damping factor

##### Q54. In a light or under damped vibrating system, the natural logarithm of the ratio of any two successive amplitudes is known as

(a) damping factor
(b) magnification factor
(c) critical damping co-efficient
(d) logarithmic decrement.

Ans:  (d) logarithmic decrement

##### Q55. The system will become torsionally equivalent when equal and opposite torque are applied to the two rotors and the system twists through an angle which is

(a) half of the angle of twist of actual shafts
(b) one-third of the angle twist of actual shafts
(c) equal to the angle of twist of actual shafts
(d) three times of the angle of twist of actual shafts.

Ans:  (c) equal to the angle of twist of actual shafts

##### Q56. In rotating horizontal shafts, there are large vibrations when the shafts are rotating at a speed which is

(a) one-fourth of critical speed
(b) one-third of critical speed
(c) one-half of critical speed
(d) two-third of critical speed.

Ans: (c) one-half of critical speed

##### Q57. The mass of spring is negligible then the natural frequency of the mass (attached to the spring)  will be

(a) less
(b) more
(c) same
(d) may be more or less

Ans:  (b) more

##### Q58. At certain speed, the rotating shaft tends to vibrate violently in transverse direction. Then speed is called

(a) whirling speed
(b) critical speed
(c) whipping speed
(d) all of the above

Ans:  (d) all of the above

##### Q59. The natural frequency of a system is a function of

(a) stiffness of the system
(b) mass of the system
(c) amplitude of oscillation
(d) both (a) and (b)

Ans:  (d) both (a) and (b)

##### Q60. The natural frequency of the free longitudinal vibrations is the

(a) same as the natural period of vibrations
(b) reciprocal of the natural period of vibrations
(c) twice the natural period of vibrations
(d) half the natural period of vibrations.

Ans:  (b) reciprocal of the natural period of vibrations

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##### Read More Sections of Theory of Machine Objective Questions

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Theory of Machine MCQ – Section-1

Theory of Machine MCQ – Section-2

Theory of Machine MCQ – Section-3

Theory of Machine MCQ – Section-4

Theory of Machine MCQ – Section-5

Theory of Machine MCQ – Section-6