Q.1
Rotating shafts tend of vibrate violently at whirling speeds because
  • the shafts are rotating at very high speeds
  • Bearing centre line coincides with the shaft axis
  • The system is unbalanced
  • Resonance is caused due to the heavy weight of the rotor
Q.2
For a harmonically excited single degree of freedom viscous damped system, which one of the following is correct?
  • Inertia force leads damping force by 90° while damping force leads spring force by 90°
  • Spring force leads damping force by 90° while damping force leads inertia force by 180°
  • Spring force and damping force are in phase, and inertia force leads them by 90°
  • Spring force and inertia force are in phase, and damping force leads them by 90°
Q.3
A spring-mass suspension has a natural frequency ofrad/s. What is the damping ratio required if it is desired to reduce this frequency torad/s by adding a damper to it?
  • 32\frac{\sqrt{3}}{2}23​​
  • 12\frac{1}{2}21​
  • 12\frac{1}{\sqrt{2}}2​1​
  • 14\frac{1}{4}41​
Q.4
Consider the following methods:Energy methodEquilibrium methodRayleigh's method Which of these methods can be used for determining the natural frequency of the free vibrations?
  • 1 & 2
  • 2 & 3
  • 3 & 1
  • 1, 2 & 3
Q.5
A uniform cantilever beam undergoes transverse vibrations. The number of natural frequencies associated with the beam is
  • 1
  • 10
  • 100
  • ∞\infty∞
Q.6
A machine mounted on a single coil spring has a period of free vibration of T. If the spring is cut into four equal parts and placed in parallel and the machine is mounted on them, then the period of free vibration of the new system will become.
  • 16T
  • 4T
  • T4\frac{T}{4}4T​
  • T16\frac{T}{16}16T​
Q.7
If air resistance is neglected, while it is executing small oscillations the acceleration of the bob of a simple pendulum at the mid-point of its swing will be
  • zero
  • a minimum but not equal to zero
  • a maximum
  • not determinable unless the length of the pendulum and the mass of the bob are known
Q.8
Under logarithmic decrement, the amplitude of successive vibrations are
  • Constant
  • in arithmetic progression
  • In geometric progression
  • in logarithmic progression
Q.9
When the mass of a critically damped single degree of freedom system is deflected from its equilibrium position and released, it will
  • return to equilibrium position without oscillation
  • Oscillate with increasing time period
  • Oscillate with decreasing amplitude
  • Oscillate with constant amplitude.
Q.10
A motion is aperiodic at what value of the damping factor?
  • 1 or above
  • 0.5
  • 0.3
  • 0.866
Q.11
In a forced vibration with viscous damping, maximum amplitude occurs when forced frequency is
  • Equal to natural frequency
  • Slightly less than natural frequency
  • Slightly greater than natural frequency
  • Zero
Q.12
The static deflection of a shaft under a flywheel is 4 mm. Take g = 10m/s2 . What is the critical speed in rad/s ?
  • 50
  • 20
  • 10
  • 5
Q.13
A vibratory system consists of a mass 12.5 kg, a spring of stiffnessN/m, and a dashpot with damping coefficient ofNs/m.The value of critical damping of the system is (Ns/m)
  • 0.223
  • 17.88
  • 71.4
  • 223.6
Q.14
In a spring-mass system, the mass is 0.1 kg and the stiffness of the spring is 1 kN/m. By introducing a damper, the frequency of oscillation is found to beof the original value. What is the damping coefficient of the damper (Ns/m)
  • 1.2
  • 3.4
  • 8.7
  • 12
Q.15
If the length of the cantilever beam is halved, then natural frequency of the mass M at the end of this, cantilever beam of negligible mass is increased by a factor of
  • 2
  • 4
  • 8
  • 8\sqrt{8}8​
Q.16
A machine ofkg mass is supported on springs of total stiffnesskN/m. Machine has an unbalanced rotating force ofN at speed ofrpm. Assuming a damping factor of 0.the value of transmissibility ratio is
  • 0.0531
  • 0.9922
  • 0.0162
  • 0.0028
Q.17
The natural frequency of an undamped vibrating system israd/s A damper with a damping factor of 0.8 is introduced into the system, The frequency of vibration of the damped system, rad/s, is
  • 60
  • 75
  • 80
  • 100
Q.18
The natural frequency of a spring-mass system on earth is N .The natural frequency of this system on the moon is
  • N
  • 0.408N
  • 0.204N
  • 0.167N
Q.19
In a multi-rotor system of torsional vibration maximum number of nodes that can occur is
  • two
  • equal to the number of rotor plus one
  • equal to the number of rotors
  • equal to the number of rotors minus one
Q.20
During torsional vibration of a shaft, the node is characterized by the
  • maximum angular velocity
  • maximum angular displacement
  • maximum angular acceleration
  • zero angular displacement
0 h : 0 m : 1 s