Question:
Whirling speed of a shaft coincide with the natural frequency of the:
Whirling speed of a shaft coincide with the natural frequency of the:
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Whirling or critical speed happens when the shaft’s rotation matches the frequency of transverse vibrations — not longitudinal or torsional.
Updated On: Jun 21, 2025
- Longitudinal vibration
- Transverse vibration
- Torsional vibration
- Coupled between torsional vibration
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The Correct Option is B
Solution and Explanation
The whirling speed (also called critical speed) of a shaft refers to the speed at which the shaft begins to vibrate violently in a transverse direction due to resonance.
This occurs when the rotational speed of the shaft matches its natural frequency of transverse (lateral) vibrations.
At this point:
- The shaft undergoes large amplitude deflections even with small initial disturbances.
- The imbalance forces become critically amplified.
Incorrect options:
- (1) Longitudinal vibration relates to axial motion, not associated with whirling.
- (3) Torsional vibration involves twisting; whirling is not caused by this.
- (4) Coupled torsional vibrations are not relevant to the definition of whirling speed.
This occurs when the rotational speed of the shaft matches its natural frequency of transverse (lateral) vibrations.
At this point:
- The shaft undergoes large amplitude deflections even with small initial disturbances.
- The imbalance forces become critically amplified.
Incorrect options:
- (1) Longitudinal vibration relates to axial motion, not associated with whirling.
- (3) Torsional vibration involves twisting; whirling is not caused by this.
- (4) Coupled torsional vibrations are not relevant to the definition of whirling speed.
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