Critical (whirling) speed of a rotating shaft: Which parameter(s) affect the critical speed? Consider a shaft with a mounted disc and small eccentricity; classical whirling theory applies. Choose the correct option.

Given data

• Parameters listed: disc diameter/mass (affects inertia), shaft span (affects stiffness), eccentricity (offset of mass center).

Concept / Approach
Critical speed depends on shaft stiffness (∝ 1/L³ for a uniform shaft), distributed/point masses, and eccentricity that excites whirl.

Reasoning
Changing any of these parameters shifts the natural frequency; therefore each affects the critical speed.

Final Answer
All of these