Q. If the volume of a sphere is increasing at a constant rate, then the rate at which its radius is increasing,is

A) a constant
B) Proportional to the radius
C) Inversely proportional to the radius
D) Inversely proportional to the surface area
Explanation

(d)
Given that, $\frac{dV}{dt} = k$ (say)
$\because\ \ \ V = \frac{4}{3}\pi R^{3}$
$\Rightarrow \ \ \ \frac{dV}{dt} = 4\pi R^{2}\frac{dR}{dt}$
$\Rightarrow \ \ \ \frac{dR}{dt} = \frac{k}{4\pi R^{2}}$
$\Rightarrow$ Rate of increasing radius is inversely proportional to its surface area

Dr. Abubacker
Reviewed by Dr. Abubacker

Physics Educator & NEET/JEE Specialist

Ph.D. in Physics with 19+ years of teaching experience.