🔍 Key Concepts

• Natural frequency of a rotating shaft and what happens when operating speed matches it • Difference between centrifugal force failure and vibration/resonance problems • Meaning of harmonic synchronism in vibration and rotating machinery

💭 Think About

• Which choice talks about the relationship between the shaft’s running speed and its own vibration characteristics, rather than just "too fast" or "too much torque"? • When engineers warn about critical speed, are they usually worried first about the shaft instantly breaking apart, or about severe resonance and vibration? • What does "harmonic synchronism" suggest: matching frequencies or being out of step?

✅ Before You Answer

• Identify which options mention natural vibration frequency or harmonic behavior. • Eliminate any options that focus only on over-torque or simple overspeed centrifugal failure with no mention of vibration or resonance. • Ask: at critical speed, is the shaft speed typically matching or not matching its natural frequency?