1. When there is a reduction in the amplitude of vibrations over every cycle of vibration, then the body is said to have

- free vibrations
- forced vibrations
- damped vibrations
- torsional vibrations

2. At a certain speed, revolving shafts tend to vibrate violently in transverse directions, this speed is known as

- critical speed
- whirling speed
- whipping speed
- All the above

3. Damping capacity of a material is its ability to

- Absorb shocks
- Absorb impact
- Withstand creep failures
- Absorb Vibrations

4. The torsional vibrational frequency of a shaft with n oscillating masses will be

- n-1
- n
- 2n
- n+1

5. In free vibrations, the acceleration vector leads the displacement vector by

- π/3
- π/2
- 2π/3
- π

6. At critical speed

- the shaft runs smoothly
- the shaft runs with noise due to vibration
- the shaft becomes dynamically unstable with negligible lateral amplitudes
- the shaft becomes dynamically unstable with

7. In a damped vibration system, the damping force is proportional to

- Vibrations
- Displacement
- Velocity
- Compression

8. In underdamped system the amplitude of vibration with reference to time

- increases linearly
- increases exponentially
- decreases linearly
- decreases exponentially

9. For steady state forced vibrations, the phase lag at resonance condition is

- 45°
- 0°
- 90°
- 80°

10. In the spring mass system, if the mass of the system is double with spring stiffness halved, the natural frequency of vibration is

- remains unchanged
- doubled
- halved
- quadrupled

11. If the period of oscillation is doubled

- the length of simple pendulum should be doubled
- the length of simple pendulum should be quadrupled
- the mass of the pendulum should be doubled
- the length and mass should be doubled

12. Seismic vibrations are measured with

- Richter scale
- Vibrometers
- Accelerometers
- Gyroscope

13. If the damping factor for a vibrating system is unity, then the system is

- critically damped
- underdamped
- zero damped
- overdamped

14. The amplitude ratio of two successive oscillations of a damped vibratory system is

- more than one
- less than one
- variable
- equal to one

15. Whirling speed of a shaft coincides with the natural frequency of the

- longitudinal vibration
- transverse vibration
- All of above
- None of the above

16. A shaft carrying two rotors as its ends will have

- no node
- one node
- two node
- three node

17. Critical speed of a shaft depends on

- Diameter of disc
- Length of shaft
- Eccentricity
- All of the above

18. A vibrating system with unity as damping factor will be

- critically damped
- damped to safe limits
- partly damped
- free from vibrations

19. Which of the following behaviour of the system defines under-damped harmonic oscillator?

- The system returns (exponentially decays) to equilibrium without oscillating.
- The system returns to equilibrium as quickly as possible without oscillating.
- The system oscillates (at reduced frequency compared to the undamped case) with the amplitude gradually decreasing to zero.
- The system oscillates at its natural resonant frequency.

20. The ratio of damping constant to the critical damping constant is called

- Logarithmic decrement
- Damping ratio
- Magnification factor
- Transmissibility ratio