Question 137Motor Plants - QMED

The correct answer is B) Critical speed. The critical speed refers to the operational speed at which excessive engine vibration is created. This is due to the engine's natural frequency matching the rotational speed, leading to resonance and amplification of vibrations. Exceeding the critical speed can result in damage to the engine and other components. The other options are incorrect: A) Non-harmonic speed is not a standard term in this context. C) Maximum speed refers to the highest sustainable speed, which may or may not coincide with the critical speed. D) Design maximum speed is the speed the engine is designed to operate at, which may be different from the critical speed.