# Critical or whirling speed is the speed at which the shaft tends to vibrate violently in ________.

By Ritesh|Updated : November 1st, 2022
1. Transverse direction
2. Longitudinal direction
3. Linear direction
4. None of these

Critical or whirling speed is the speed at which the shaft tends to vibrate violently in the transverse direction. The whirling speed or crucial speed of a shaft is the speed at which a rotating shaft will normally begin to vibrate violently in the transverse direction if the shaft rotates in the horizontal plane. In other words, resonance occurs at the spinning speed, also referred to as the critical speed.

### Critical or Whirling Speed of Shaft

• Resonance occurs when the system's natural frequency and the frequency of the external force are in phase.
• The crucial speeds, whirling speeds, or whipping are the speeds at which resonance occurs. The shaft vibrates vigorously in the transverse direction and its deviation from the axis of rotation becomes infinite when it runs at this speed.
• The object starts to resonate when the speed of rotation approaches its natural frequency, which significantly raises system vibration. No matter how the resonance is oriented, it happens. The rotational speed is referred to as the crucial speed when it reaches the natural vibration's numerical value.

The following determines how much deflection there will be:

• The shaft's stiffness and support
• total weight of the shaft and its attachments
• the imbalance between the mass and the axis of rotation
• The system's damping percentage

Summary:

## Critical or whirling speed is the speed at which the shaft tends to vibrate violently in ________. (a) Transverse direction (b) Longitudinal direction (c) Linear direction (d) None of these

The speed at which the shaft begins to violently vibrate in the transverse direction is known as the critical speed or whirling speed. The critical speed is the theoretical angular velocity that excites the natural frequency of a spinning device, such as a shaft, propeller, lead screw, or gear, in the field of rotor dynamics of solid mechanics.