એક ઘરની છત પર રહેલી \(750\,cm^{2}\) ક્ષેત્રફળ ધરાવતી પાણીની ટાંકીમાં પાણીનું લેવલ પાઈપ ઉપર નળના સ્તરથી ઊંચે રહેલ છે. \(500\,nm^2\) આડછેદનું ક્ષેત્રફળ ધરાવતો નળ જ્યારે ખુલ્લો હોય ત્યારે નળમાંથી બાહર નીકળતા પાણીનો વેગ \(30\,cm/s\) છે. આ સમયે \(\frac{dh}{dt}\) નું મૂલ્ય \(x \times 10^{-3}\,m/s\) છે. \(x\) નું મૂલ્ય \(...........\) હશે.

A \(3\)
B \(4\)
C \(6\)
D \(2\)

Verified Solution

Answer & Solution

Correct Answer

(D) \(2\)

Step-by-step Solution

Detailed explanation

\(A _1 V _1= A _2 V _2\) \(750 \times 10^{-4} V _1=500 \times 10^{-6} \times 0.3\) \(V _1=\frac{500 \times 3 \times 10^{-3}}{750}\,m / s\) \(=2 \times 10^{-3}\,m / s\) \(\frac{ dh }{ dt }=-2 \times 10^{-3}\,m / s\)

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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