Thirteen Viva Questions on Vibrations
Q.1. Define vibration.
Answer.
When a particle goes on one side from mean position and returns back and then it goes to other side and again returns back, then it is known as one vibration. In other words, to and fro motion of a particle about a fixed point is known as vibration.
Q.2. Name different types of vibrations.
Answer.
There are three important types of vibrations from subject point of view:
- Free or natural vibrations,
- Damped vibrations,
- Force vibrations.
Q.3. Define free vibrations.
Answer.
If the vibrations of a particle after giving it an initial displacement remain continued, then the vibrations are called free or natural vibrations. No external force acts on the particle. In other words, the vibrations of the particle with fundamental frequency under the influence of the restoring force are called free vibrations.
Q.4. Define damped vibrations.
Answer.
The vibrations of a body whose amplitude goes on reducing over every cycle of vibrations are known as damped vibrations. This is due to the fact that a certain amount of energy possessed by the vibrating body is always dissipated in overcoming frictional resistance to the motion.
Q.5. Define forced vibrations.
Answer.
When the body vibrates under the influence of external periodic force, then the vibrations are known as forced vibrations.
The body does not vibrate with its natural frequency, but it vibrates with the frequency of the driver.
Q.6. Define resonance.
Answer.
When the frequency of external force is equal to the natural frequency of the vibrations, resonance takes place, amplitude or deformation or displacement will reach to its maximum at resonance and the system will fail due to breakdown. This state of disturbing force on the vibrating body is known as the state of resonance.
Q.7. Define time period related to vibratory motion.
Answer.
The time interval after which the motion is repeated itself is called time period. It is usually expressed in seconds.
Q.8. Define time cycle related to vibratory motion.
Answer.
The motion completed during one time period is called cycle.
Q.9. Define frequency related to vibratory motion.
Answer. The number of cycles executed in one second is called frequency. It is usually expressed in hertz (Hz).
Q.10. Name different types of free vibrations.
Answer.
There are three types of free vibrations:
- Longitudinal vibrations,
- Transverse vibrations,
- Torsional vibrations.
Q.11. Define longitudinal vibrations.
Answer.
Longitudinal Vibrations
When the particles of bar or disc move parallel to the axis of the shaft, then the vibrations are called longitudinal vibrations.
Q.12. Define transverse vibrations.
Answer.
Transverse Vibrations
When the particles of the bar or disc move approximately perpendicular to the axis of the shaft on either side in the transverse direction, then the vibrations are known as transverse vibrations.
Q.13. Define torsional vibrations.
Answer.
Torsional vibrations
When the particles of the bar or disc get alternately twisted and untwisted on account of vibratory motion of suspended body, it is said to be undergoing torsional vibrations.
One Response to “Thirteen Viva Questions on Vibrations”
Sasan
in forced vibration with multi degree of freedom without damping, when frequency equal natrural frequency but resonance not happen?