Question

the radius of a sheridan balloon is increasing at a rate of 3 centimeters per minute. how fast is the volume changing when the radius is 14 centimeters? v=(4/3)(pi)r^3

Answer 1

The volume of the balloon is $2352\pi cc/min$

Explanation:

The radius of the balloon is increasing at a rate of 3 cm/min.

To determine the volume of the balloon when the radius is 14 cm, we shall use the formula $V=\frac{4}{3} \pi r^3$

The rate of change of r with respect to time t is given by,

$\frac{d}{d t}(r)=3 \mathrm{cm} / \mathrm{minute}$

Now, we shall determine the $\frac{d}{d t}(V)$

$\begin{aligned}\frac{d}{d t}(V) &=\frac{d}{d t}\left(\frac{4}{3} \pi r^{3}\right) \\&=\frac{4}{3} \pi\left(3 r^{2}\right)\frac{d}{d t}(r) \\&=4 \pi r^{2}\frac{d}{d t}(r)\end{aligned}$

Now, we shall determine the $\frac{d}{d t}(V)$ at $r=14 \mathrm{cm}$ and substituting $\frac{d}{d t}(r)=3 \mathrm{cm} / \mathrm{minute}$, we get,

$\begin{aligned}\left(\frac{d V}{d t}\right)_{r=14} &=4 \pi r^{2} \frac{d}{d t}(r)\\&=4 \pi(14)^{2} (3)\\&=4 \pi 196 (3)\\&=2352\end{aligned}$

Thus, The volume of the balloon is $2352\pi cc/min$