Q.1
3d2xdy2+9dxdy+27x=03\frac{\text{d}^2x}{\text{d}y^2}+9\frac{\text{d}x}{\text{d}y}+27x=03dy2d2x​+9dydx​+27x=is the equation of motion for a damped viscous vibration. The damping factor is
  • 0.25
  • 0.5
  • 0.75
  • 1.0
Q.2
Transmissibility is unity at two points. Which one of the following is true for these two points? r=\frac{\omega}{\omega_n}r=ωn​ω​
  • r is zero and  $\sqrt{3}$  for all values of damping
  • r is zero and  $\sqrt{2}$  for all values of damping
  • r is unity and  $\sqrt{3}$  for all values of damping
  • r is unity and  $\sqrt{2}$  for all values of damping
Q.3
For steady-state forced vibrations, the phase lag at resonance is
  • $0\degree$
  • $45\degree$
  • $90\degree$
  • $180\degree$
Q.4
A viscous damping system with free vibrations will be critically damped if the damping factor is
  • Zero
  • Less than one
  • Equal to one
  • Greater than one
Q.5
When a shaking force is transmitted through the spring, damping becomes less than the applied force when the ratio of its frequency to the natural frequency is greater than
  • 0.25
  • 0.5
  • 1
  • $\sqrt{2}$
Q.6
A vehicle suspension system consists of a spring and a damper. The stiffness of the spring is 3.6 kN/m and constant of the damper isNs/m. If the mass iskg, then the damping factor and damped natural frequency (in Hz), respectively, are
  • 0.471 and 1.19 Hz
  • 0.471 and 7.48 Hz
  • 0.666 and 1.35 Hz
  • 0.666 and 8.5 Hz
Q.7
A vibrating machine is isolated from the floor using springs. If the ratio of excitation frequency of vibration of machine to the natural frequency of the isolation system is equal to 0.then transmissibility of ratio of isolation is
  • 1/2
  • 3/4
  • 4/3
  • 2
Q.8
A uniform rigid rod of mass m = 1 kg and length L = 1 m is hinged at its centre and laterally supported at one end by a spring of constant k =N/m. The natural frequency ( in rad/s) is
  • 10
  • 20
  • 30
  • 40
Q.9
A mass M attached to a light spring oscillates with a period of 2 sec. If the mass is increased by 2 kg, the period increases by 1sec. The value of M (in Kg) is
  • 1
  • 1.6
  • 2
  • 2.4
Q.10
A slender shaft supported on two bearings at its ends carries a disc with an eccentricity e from the axis of rotation. The critical speed of the shaft is N. If the disc is replaced by a second one of same weight but mounted with an eccentricity 2e, critical speed of the shaft in the second case is
  • NNN
  • 2N2N2N
  • $\frac{N}{2}$
  • $\frac{N}{\sqrt{2}}$
Q.11
The critical speed of a rotating shaft depends upon
  • Mass
  • stiffness
  • mass and stiffness
  • mass, stiffness and eccentricity
Q.12
The rotor of a turbine is generally rotated at
  • the critical speed
  • a speed much below the critical speed
  • a speed much above the critical speed
  • a speed having no relation to critical speed
Q.13
A shaft ofmm diameter and 1 m length carries a disc which has mass eccentricity equal tomicrons. The displacement of the shaft at a speed which isof critical speed in microns is
  • 810
  • 900
  • 800
  • 820
Q.14
An automotive engine weighingkg is supported on four springs with linear characteristics. Each of the front two springs have a stiffness ofMN/m while the stiffness of each rear spring isMN/m. The engine speed (in rpm), at which resonance is likely to occur, is
  • 6040
  • 3020
  • 1424
  • 955
Q.15
In a system subjected to damped forced vibrations, the ratio of maximum displacement to the static deflection is known as
  • Critical damping ratio
  • Damping factor
  • Logarithmic decrement
  • Magnification factor
Q.16
A shaft has two heavy rotors mounted on it. The transverse natural frequencies, considering each of the rotors separately, arecycles/sec andcycles/sec respectively. The lowest critical speed is
  • 5367 rpm
  • 6000 rpm
  • 9360 rpm
  • 12000rpm
Q.17
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.18
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.19
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?
  • $\frac{1}{2}$
  • $\frac{\sqrt{3}}{2}$
  • $\frac{1}{\sqrt{2}}$
  • $\frac{1}{4}$
Q.20
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
0 h : 0 m : 1 s