Question:easy

The impeller speed of a centrifugal pump is increased by 30%. The power requirement of the pump increases by \(n\) times. The value of \(n\) is ________. (Rounded off to two decimal places)

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Recall how pump power scales with impeller speed under the pump affinity laws.
Updated On: Aug 6, 2026
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Correct Answer: 2.2

Solution and Explanation

Step 1: Take logs of the affinity law.
Since $P \propto N^3$, the ratio of powers satisfies $\ln n = 3 \ln\left(\dfrac{N_2}{N_1}\right)$.

Step 2: Insert the speed increase.
Here $\dfrac{N_2}{N_1} = 1.30$, and $\ln(1.30) = 0.2624$.
$\ln n = 3 \times 0.2624 = 0.7871$.

Step 3: Undo the logarithm.
$n = e^{0.7871} = 2.197$.

Final Answer:
This confirms the power goes up by close to 2.20 times, agreeing with the direct cube calculation. \[ \boxed{n \approx 2.20} \]
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