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AP EAMCET · Maths · Application of Derivatives

If the surface area of a spherical bubble is increasing at the rate of \(4 \mathrm{sq}. \mathrm{cm} / \mathrm{sec}\), then the rate of change in its volume (in cubic \(\mathrm{cm} / \mathrm{sec}\) ) when its radius is 8 cms is

  1. A \(8\)
  2. B \(12\)
  3. C \(15\)
  4. D \(16\)
Verified Solution

Answer & Solution

Correct Answer

(D) \(16\)

Step-by-step Solution

Detailed explanation

\(A = 4\pi r^2\) \(\frac{dA}{dt} = 8\pi r \frac{dr}{dt}\) \(4 = 8\pi (8) \frac{dr}{dt} \implies \frac{dr}{dt} = \frac{1}{16\pi}\) \(V = \frac{4}{3}\pi r^3\) \(\frac{dV}{dt} = 4\pi r^2 \frac{dr}{dt}\) \(\frac{dV}{dt} = 4\pi (8)^2 \left(\frac{1}{16\pi}\right)\)…