If the water is being poured at the rate $36 \mathrm{~m}^3 / \mathrm{sec}$ in cylindrical vessel of base…

If the water is being poured at the rate $36 \mathrm{~m}^3 / \mathrm{sec}$ in cylindrical vessel of base radius $3 \mathrm{~m}$, then the rate at which water level is rising, is
  1. $\frac{4}{\pi} \mathrm{m} / \mathrm{sec}$
  2. $4 \pi \mathrm{m} / \mathrm{sec}$
  3. $\frac{\pi}{4} \mathrm{~m} / \mathrm{sec}$
  4. $\frac{3}{\pi} \mathrm{m} / \mathrm{sec}$

Solution

$\frac{\mathrm{d} v}{\mathrm{~d} t}=36 \mathrm{~m}^3 / \mathrm{sec}$ and $v=\pi r^2 \mathrm{~h}=\pi \times 3^2 \mathrm{~h}=9 \pi \mathrm{h}$ $\Rightarrow \frac{\mathrm{d} v}{\mathrm{~d} t}=9 \pi \frac{\mathrm{d} h}{\mathrm{~d} t}$ $\Rightarrow 36=9 \pi \frac{\mathrm{d} h}{\mathrm{~d} t}$ $\Rightarrow \frac{\mathrm{d} h}{\mathrm{~d} t}=\frac{4}{\pi} \mathrm{m} / \mathrm{sec}$

Asked in: MHT CET 2022 (08 Aug Shift 1)

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