VIBRATIONS MULTIPLE CHOICE QUESTIONS (MCQ) WITH ANSWERS
VIBRATIONS MULTIPLE CHOICE
QUESTIONS (MCQ) WITH
ANSWERS
MCQ increases depth of understanding. It
gives a high degree of clarity. Vibration is
a periodic motion. It is like reversal
loading. It is highly dangerous. Vibrations
are free & forced vibrations with /without
damping. Vibrations causes unpleasant
sound. It weakens the foundation of a
structure.
Fig. Longitudinal Free Vibrations
Fig. Vibration representation as a sin wave
Fig. Forced Undamped Vibrations
Fig. Forced Damped Vibrations
Fig. Representation of Forced & Free Vibrations
Fig. Damped Vibrations
Fig. Vibration reductions
Vibration reduction systems
a) Machine bolted to a rigid foundation
b) Supported on isolation springs, rigid foundation,
c) Machine attached to an inertial mass
d) Machine supported on isolation springs at two levels with a seismic mass in between
Fig Spring Vibrations

The most salient features of any vibration are

Amplitude & acceleration

Frequency & acceleration

Amplitude & frequency

None

ANS: (c)

One Hertz is equal to

3 cycles per second

6 cycles per second

9 cycles per second

None
ANS: (d)

One Hertz means

3 cycles per second

1 cycle per second

2 cycles per second

None
ANS: (b)

During vibration, speed of motion is

Constant

Variable

Can’t say

None
ANS: (b)

During each cycle of vibration, the magnitude of acceleration range as the object moves from its stationary position

Firstly 0 to 10 m/s^{2}

Secondly 0 to 20 m/s^{2}

Thirdly 0 to maximum

None
ANS: (c)

A structure under vibration is under

Constant load

Variable load

Reversing load

None
ANS: (c)

A reversing load

Increases the strength

Decreases the strength

Do not affect the strength

None
ANS: (b)

Acceleration of a vibration is zero at the

Extreme left

Extreme right

Mean position

None
ANS: (c)

Vibration is a phenomenon

Mechanical

Electrical

Civil

None
ANS: (a)

Vibrations are

Desirable

Undesirable

Both (a) & (b)

None
ANS: (c)

The desirable vibrations is in a

Mobile phone

Moving electric motor

Moving engine

None
ANS: (a)

The undesirable vibration is in a

Mobile phone

Electric motor

Both (a) & (b)

None
ANS: (b)

The vibrations is

Periodic

Random

Both (a) & (b)

None
ANS: (c)

Types of vibrations are

Free & forced

Damped

Both (a) & (b)

None
ANS: (c)

Identify a free vibration

Pulling a child back on a swing

Hitting a tuning fork

Both (a) & (b)

None
ANS: (c)

Identify a forced vibration

Pulling a child back on a swing

Vibration of a building due to earthquake

Both (a) & (b)

None
ANS: (b)

Identify a damped vibration

Vibration of a vehicle on an uneven road

Vehicular suspension system

Both (a) & (b)

None
ANS: (b)

Free vibration of a mechanical system comes from

Individual disturbance

Continuous disturbance

Both (a) & (b)

None
ANS: (a)

Forced vibration of a mechanical comes from

Single disturbance

Continuous disturbance

Both single and continuous disturbance

None
ANS: (b)

A damped vibration of a mechanical comes from a

Shock absorber

Friction

Both shock absorber & friction

None
ANS: (c)

Low frequency vibration is

> 100 HZ

<100 HZ

> 2000HZ

None
ANS: (b)

High frequency vibration is of

<100 HZ

> 2000 HZ

≤ 2000 HZ

None
ANS: (c)

In mechanical vibrations, it is desirable to achieve

Resonance

Antiresonance

Can’t say

None
ANS: (b)

Identify the equation of natural frequency

f =(1/π) (k/m)^{5}

f =(1/3π)(k/m)^{5}

f=(1/4π)(k/m))^{5}

None
ANS: (d)

Identify the equation of natural frequency

f =(1/4π) (k/m)^{5}

f =(1/6π)(k/m)^{5}

f=(1/2π)(k/m))^{5}

None

ANS: (c)

Identify the equation of natural frequency

F =(1/π) (k/m)^{5}

F =(1/3π)(k/m)^{5}

F=(1/4π)(k/m))^{5}

None
ANS: (d)

Damping force is proportional to the

Displacement

Velocity

Acceleration

None
ANS: (b)

In the absence of a damping, the vibration will stop

After 10 minutes

Immediately

Never

None
ANS: ©

Vibration produces sound. Sound includes the vibrations of the

Object and air molecules

Eardrum

Both (a) & (b)

None
ANS: (c)

The slowest vibration frequency the human ear hears is

10 HZ

20 HZ

100 Hz

None
ANS: (b)

The fastest vibration frequency the human ear hears is

1lac HZ

3 lac HZ

2 lac Hz

None
ANS: (c)

Vibrations exists in

Inelastic bodies

Elastic bodies

Both elastic & inelastic bodies

None
ANS: (b)

Vibration is a friend in a

Compressor

Pneumatic drill

Both compressor & pneumatic drill

None
ANS: (b)

Vibration is a foe in a

Compressor

Pneumatic drill

Both compressor & pneumatic drill

None
ANS: (a)

Periodic motion is that motion which repeats itself after

Different intervals of time

Equal intervals of time

Both equal and different intervals of time

None
ANS: (b)

Time taken for one complete vibration is time period in

Hours

Minutes

Seconds

None
ANS: (c)

Simple harmonic motion is motion of a particle with time in a circle with uniform

Tangential velocity

Axial velocity

Radial velocity

None
ANS: (a)

The natural frequency of a system is the

Forced vibrations

Damped vibrations

Free vibrations

None
ANS: (c)

Natural frequency of a certain system is

Variable

Constant

Variable and constant

None
ANS: (b)

Resonance produces when vibration of a system under an external force is equal to the

Four times the natural frequency

Two times the natural frequency

Three times the natural frequency

None
ANS: (d)

The amplitude of vibration at resonance is

Very small

Very large

Average

None
ANS: (b)

At resonance condition with minimum input, output is

Medium

Minimum

Maximum

None
ANS: (c)

Damping keeps vibrations

Constant

Decreases

Increases

None
ANS: (b)

Types of free vibrations are

Longitudinal & Transverse

Transverse & torsional

Longitudinal, transverse & torsional

None
ANS: (c)

The free vibrations means no time varying

External force acts

Internal force acts

Both (a) & (b)

None
ANS: (a)

Time ‘ T ‘ required to complete one vibration is

T=2π ω_{0}

T =2π + ω_{0}

T =2π /ω_{0}

None
ANS: (c)

The natural frequency ‘ ω_{0} ‘ of free vibration is

Firstly ω_{o} =(k/m)

Secondly ω_{o} =(k/m) ^{45}

Thirdly ω_{o} =(k/m)^{5}

None
ANS: (c)

The differential equation for free undamped vibration for mass ‘m’ , spring stiffness ’k’ & displacement ‘x’ from the equilibrium position is

Firstly m d^{2}x/d^{2}t +k x =C

Secondly m d^{2}x/d^{2}t +k x =0

Thirdly m d^{2}x/d^{2}t +k^{2} x =0

None
ANS: (b)

The solution of free undamped vibration equation ‘m d^{2}x/d^{2}t +k x =0 is

Firstly x=2A Cos (k/m)^{5} + B Sin (k/m)^{0.5}

Secondly x=A Cos (k/m)^{5} + 2B Sin (k/m)^{0.5}

Thirdly x=A Cos (k/m)^{5} + B Sin (k/m)^{0.5}

None
ANS: (c)

Critical damping coefficient is

Firstly C_{c} = 2(k m)^{5}

Secondly C_{c} = 2km

Thirdly C_{c}=2 k/m

None
ANS: (a)

The differential equation for free vibrations with viscous damping coefficient ‘c’ is

Firstly m d^{2}x/d^{2}t +c + k x =C

Secondly m d^{2}x/d^{2}t +c dx/dt +k x =0

Thirdly m d^{2}x/d^{2}t +cx +k^{2} x =0

None

ANS: (b)

Damping is less than critical damping. Then solution of the differential equation m d^{2}x/d^{2}t +c dx/dt +k x =0 with damped natural frequency’ ω_{d} ‘ is

Firstly x = e^{c t/m} (A Sin ω_{d} t +B Cos ω_{d}t)

Secondly x = e^{c t/2m} (A Sin ω_{d} t +B Cos ω_{d}t)

Thirdly x = e^{c t/4m} (A Sin ω_{d} t +B Cos ω_{d}t)

None
ANS: (b)

The relation of damped natural and undamped natural frequency is

Firstly ω_{d} = ω_{0} (1ζ ) ^{5}

Secondly ω_{d} = ω_{0} (1ζ ^{3} )^{5}

Thirdly ω_{d} = ω_{0} (1ζ ^{2} )^{5}

None
ANS: (c)

Solution of the differential equation m d^{2}x/d^{2}t +c dx/dt +k x =0 with damped natural frequency’ ω_{d} ‘ and critical damping is

Firstly x = e^{c t/m} (A Sin ω_{d} t +B Cos ω_{d}t)

Secondly x = e^{c t/2m} (A +Bt)

Thirdly x = e^{c t/4m} (A – Bt)

None
ANS: (b)
55. Differential equation of forced vibration with Sinusoidal force = F_{0} Sin ωt ‘ without damping is

Firstly m d^{2}x/d^{2}t +k x =C F_{0} Sin ωt

Secondly m d^{2}x/d^{2}t +k x =C

Thirdly m d^{2}x/d^{2}t +k^{2} x = F_{0} Sin ωt

None
ANS: (c)
56. Differential equation of forced vibration with Sinusoidal force = F_{0} Sin ωt ‘ with damping is

Firstly m d^{2}x/d^{2}t +c dx/dt + k x = F_{0} Sin ωt

Secondly m d^{2}x/d^{2}t + c dx/dt + k x =C

Thirdly m d^{2}x/d^{2}t +c dx/dt + k^{2} x = F_{0} Sin ωt

None
ANS: (a)
57. Vibrations cause
(a) Structural failure
(b) mechanical failure
(c) Both (a) & (b)
(d) None
ANS: (c )
58. Vibration cause in a moving machinery
(a) Disappearance of a crack
(b) Appearance of a crack
(c) Both (a) & (b)
(d) None
ANS: (b)
59. Vibrations cause in a moving machine
(a) Tightening of fasteners
(b) Loosening of fasteners
(c) Braking of fasteners
(d) None
ANS: (b)
60. Which natural calamity causes dangerous vibrations?
(a) Floods
(b) Cyclone
(c) Earthquake
(d) None
ANS: (c )