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Forcing Frequency and Resonance

In firefighting vertical water pump, an hydraulic turbulence can exert alternating dynamic forces on the vertical structure. Statement-1: The frequencies of these dynamic forces are independent on the speed of the pump. Statement-2: When the frequency of dynamic forces matches the natural frequency of a pump component, the resonant vibration will occur.
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Answer & Explanation
Correct AnswerC. Statement-1 is False, but Statement-2 is True

Quick Explanation

Hydraulic excitation frequencies in a vertical pump are linked to rotational speed, blade passing and flow phenomena, so they are not independent of pump speed. Resonance occurs when an excitation frequency coincides with a structural natural frequency. Thus statement 1 is false and statement 2 is true: option C.

Formula / Key Relation

Resonance: fforcing ≈ fnatural
Forcing Frequency and Resonance explanatory diagram

Detailed Explanation

Correct Answer

C — Statement-1 is False, but Statement-2 is True

Statement-wise Analysis

Statement 1: False

Statement 2: True

Concept and Reasoning

Hydraulic excitation frequencies in a vertical pump are linked to rotational speed, blade passing and flow phenomena, so they are not independent of pump speed. Resonance occurs when an excitation frequency coincides with a structural natural frequency. Thus statement 1 is false and statement 2 is true: option C.

Calculation / Key Relation

Resonance: fforcing ≈ fnatural

Exam Takeaway

Pump speed changes forcing frequency; resonance is frequency matching.

Common Mistake

Do not assume hydraulic forcing has a fixed frequency independent of shaft speed.

Quick Trick

Pump speed changes forcing frequency; resonance is frequency matching.

Common Mistake

Do not assume hydraulic forcing has a fixed frequency independent of shaft speed.

Exam Tip

Pump speed changes forcing frequency; resonance is frequency matching.

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