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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
  1. The most salient features of any vibration are

    1. Amplitude & acceleration
    2. Frequency & acceleration
    3. Amplitude & frequency
    4. None
ANS: (c)
  1. One Hertz is equal to

  1. 3 cycles per second
  2. 6 cycles per second
  3. 9 cycles per second
  4. None
ANS: (d)
  1. One Hertz means

  1. 3 cycles per second
  2. 1 cycle per second
  3. 2 cycles per second
  4. None
ANS: (b)
  1. During vibration, speed of motion is

  1. Constant
  2. Variable
  3. Can’t say
  4. None
ANS: (b)
  1. During each cycle of vibration, the magnitude of acceleration range as the object moves from its stationary position

  1. Firstly                       0 to 10 m/s2
  2. Secondly                  0 to 20 m/s2
  3. Thirdly                     0 to maximum
  4. None
ANS: (c)
  1. A structure under vibration is under

  1. Constant load
  2. Variable load
  3. Reversing load
  4. None
ANS: (c)
  1. A reversing load

  1. Increases the strength
  2. Decreases the strength
  3. Do not affect the strength
  4. None
ANS: (b)
  1. Acceleration of a vibration is zero at the

  1. Extreme left
  2. Extreme right
  3. Mean position
  4. None
ANS: (c)
  1. Vibration is a phenomenon

  1. Mechanical
  2. Electrical
  3. Civil
  4. None
ANS: (a)
  1. Vibrations are

  1. Desirable
  2. Undesirable
  3. Both (a) & (b)
  4. None
ANS: (c)
  1. The desirable vibrations is in a

  1. Mobile phone
  2. Moving electric motor
  3. Moving engine
  4. None
ANS: (a)
  1. The undesirable vibration is in a

  1. Mobile phone
  2. Electric motor
  3. Both (a) & (b)
  4. None
ANS: (b)
  1. The vibrations is

  1. Periodic
  2. Random
  3. Both (a) & (b)
  4. None
ANS: (c)
  1. Types of vibrations are

  1. Free & forced
  2. Damped
  3. Both (a) & (b)
  4. None
ANS: (c)
  1. Identify a free vibration

  1. Pulling a child back on a swing
  2. Hitting a tuning fork
  3. Both (a) & (b)
  4. None
ANS: (c)
  1. Identify a forced vibration

  1. Pulling a child back on a swing
  2. Vibration of a building due to earthquake
  3. Both (a) & (b)
  4. None
ANS: (b)
  1. Identify a damped vibration

  1. Vibration of a vehicle on an uneven road
  2. Vehicular suspension system
  3. Both (a) & (b)
  4. None
ANS: (b)
  1. Free vibration of a mechanical system comes from

  1. Individual disturbance
  2. Continuous disturbance
  3. Both (a) & (b)
  4. None
ANS: (a)
  1. Forced vibration of a mechanical comes from

  1. Single disturbance
  2. Continuous disturbance
  3. Both single and continuous disturbance
  4. None
ANS: (b)
  1. A damped vibration of a mechanical comes from a

  1. Shock absorber
  2. Friction
  3. Both shock absorber & friction
  4. None
ANS: (c)
  1. Low frequency vibration is

  1. > 100 HZ
  2. <100 HZ
  3. > 2000HZ
  4. None
ANS: (b)
  1. High frequency vibration is of

  1. <100 HZ
  2. > 2000 HZ
  3. ≤ 2000 HZ
  4. None
ANS: (c)
  1. In mechanical vibrations, it is desirable to achieve

  1. Resonance
  2. Anti-resonance
  3. Can’t say
  4. None
ANS: (b)
  1. Identify the equation of natural frequency

  1. f =(1/π) (k/m)5
  2. f =(1/3π)(k/m)5
  3. f=(1/4π)(k/m))5
  4. None
ANS: (d)
  1. Identify the equation of natural frequency

    1. f =(1/4π) (k/m)5
    2. f =(1/6π)(k/m)5
    3. f=(1/2π)(k/m))5
    4. None
ANS: (c)
  1. Identify the equation of natural frequency

  1. F =(1/π) (k/m)5
  2. F =(1/3π)(k/m)5
  3. F=(1/4π)(k/m))5
  4. None
ANS: (d)
  1. Damping force is proportional to the

  1. Displacement
  2. Velocity
  3. Acceleration
  4. None
ANS: (b)
  1. In the absence of a damping, the vibration will stop

  1. After 10 minutes
  2. Immediately
  3. Never
  4. None
ANS: ©
  1. Vibration produces sound. Sound includes the vibrations of the

  1. Object and air molecules
  2. Eardrum
  3. Both (a) & (b)
  4. None

ANS: (c)

  1. The slowest vibration frequency the human ear hears is

  1. 10 HZ
  2. 20 HZ
  3. 100 Hz
  4. None
ANS: (b)
  1. The fastest vibration frequency the human ear hears is

  1. 1lac HZ
  2. 3 lac HZ
  3. 2 lac Hz
  4. None
ANS: (c)
  1. Vibrations exists in

  1. Inelastic bodies
  2. Elastic bodies
  3. Both elastic & inelastic bodies
  4. None
ANS: (b)
  1. Vibration is a friend in a

  1. Compressor
  2. Pneumatic drill
  3. Both compressor & pneumatic drill
  4. None
ANS: (b)
  1. Vibration is a foe in a

  1. Compressor
  2. Pneumatic drill
  3. Both compressor & pneumatic drill
  4. None
ANS: (a)
  1. Periodic motion is that motion which repeats itself after

  1. Different intervals of time
  2. Equal intervals of time
  3. Both equal and different intervals of time
  4. None

ANS: (b)

  1.  Time taken for one complete vibration is time period in

  1. Hours
  2. Minutes
  3. Seconds
  4. None
ANS: (c)
  1. Simple harmonic motion is motion of a particle with time in a circle with uniform

  1.  Tangential velocity
  2.  Axial velocity
  3. Radial velocity
  4. None
ANS: (a)
  1. The natural frequency of a system is the

  1. Forced vibrations
  2. Damped vibrations
  3. Free vibrations
  4. None
ANS: (c)
  1. Natural frequency of a certain system is

  1. Variable
  2. Constant
  3. Variable and constant
  4. None
ANS: (b)
  1. Resonance produces when vibration of a system under an external force is equal to the

  1. Four times the natural frequency
  2. Two times the natural frequency
  3. Three times the natural frequency
  4. None
ANS: (d)
  1. The amplitude of vibration at resonance is

  1. Very small
  2. Very large
  3. Average
  4. None

ANS: (b)

  1. At resonance condition with minimum input, output is

  1. Medium
  2. Minimum
  3. Maximum
  4. None
ANS: (c)
  1. Damping keeps vibrations

  1. Constant
  2. Decreases
  3. Increases
  4. None
ANS: (b)
  1. Types of free vibrations are

  1. Longitudinal & Transverse
  2. Transverse & torsional
  3. Longitudinal, transverse & torsional
  4. None
ANS: (c)
  1. The free vibrations means no time varying

  1. External force acts
  2. Internal force acts
  3. Both (a) & (b)
  4. None
ANS: (a)
  1. Time ‘ T ‘ required to complete one vibration is

  1. T=2π ω0
  2. T =2π + ω0
  3. T =2π /ω0
  4. None
ANS: (c)
  1. The natural frequency ‘ ω0 ‘ of free vibration is

  1. Firstly                        ωo =(k/m)
  2. Secondly                    ωo =(k/m) 45
  3. Thirdly                       ωo =(k/m)5
  4. None
ANS: (c)
  1. The differential equation for free undamped vibration for mass ‘m’ , spring stiffness ’k’ & displacement ‘x’ from the equilibrium position is

  1. Firstly                                      m d2x/d2t +k x =C
  2. Secondly                                  m d2x/d2t +k x =0
  3. Thirdly                                      m d2x/d2t +k2 x =0
  4. None
ANS: (b)
  1. The solution of free undamped vibration equation ‘m d2x/d2t +k x =0 is

  1. Firstly                                  x=2A Cos (k/m)5 + B Sin (k/m)0.5
  2. Secondly                              x=A Cos (k/m)5 + 2B Sin (k/m)0.5
  3. Thirdly                                  x=A Cos (k/m)5 + B Sin (k/m)0.5
  4. None
ANS: (c)
  1. Critical damping coefficient is

  1. Firstly                        Cc = 2(k m)5
  2. Secondly                   Cc = 2km
  3. Thirdly                      Cc=2 k/m
  4. None
ANS: (a)
  1. The differential equation for free vibrations with viscous damping coefficient ‘c’ is

    1. Firstly                               m d2x/d2t +c + k x =C
    2. Secondly                          m d2x/d2t +c dx/dt +k x =0
    3. Thirdly                              m d2x/d2t +cx +k2 x =0
    4. None
ANS: (b)
  1. Damping is less than critical damping. Then solution of the differential equation m d2x/d2t +c dx/dt +k x =0 with damped natural frequency’ ωd ‘ is

  1. Firstly                          x = e-c t/m (A Sin ωd t +B Cos ωdt)
  2. Secondly                     x = e-c t/2m (A Sin ωd t +B Cos ωdt)
  3. Thirdly                        x = e-c t/4m (A Sin ωd t +B Cos ωdt)
  4. None
ANS: (b)
  1. The relation of damped natural and undamped natural frequency is

  1. Firstly                              ωd = ω0 (1-ζ ) 5
  2. Secondly                            ωd = ω0 (1-ζ 3 )5
  3. Thirdly                                ωd = ω0 (1-ζ 2 )5
  4. None
ANS: (c)
  1. Solution of the differential equation m d2x/d2t +c dx/dt +k x =0 with damped natural frequency’ ωd ‘ and critical damping is

  1. Firstly                                       x = e-c t/m (A Sin ωd t +B Cos ωdt)
  2. Secondly                                   x = e-c t/2m (A +Bt)
  3. Thirdly                                      x = e-c t/4m (A – Bt)
  4. None
ANS: (b)

55. Differential equation of forced vibration with Sinusoidal force = F0 Sin ωt ‘ without damping is

  1. Firstly                                  m d2x/d2t +k x =C F0 Sin ωt
  2. Secondly                             m d2x/d2t +k x =C
  3. Thirdly                                 m d2x/d2t +k2 x = F0 Sin ωt
  4. None

ANS: (c)

56. Differential equation of forced vibration with Sinusoidal force = F0 Sin ωt ‘ with damping is

  1. Firstly                                  m d2x/d2t +c dx/dt + k x = F0 Sin ωt

  2. Secondly                             m d2x/d2t + c dx/dt + k x =C

  3. Thirdly                                 m d2x/d2t +c dx/dt + k2 x = F0 Sin ωt

  4. 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 )

 

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