A spherical snowball is melting in such a way that it maintains its shape. The snowball is decreasing in volume at a constant rate of 8 cubic centimeters per hour. At what rate, in centimeters per hour, is the radius of the snowball decreasing at the instant when the radius is 10 centimeters? (The volume of a sphere of radius r is v = 4/3 πr3 .)

Respuesta :

The radius of the snowball is decreasing at a rate 6.37 x 10⁻³ cm/hr

Explanation:

We have volume of sphere given by

           [tex]V=\frac{4}{3}\pi r^3[/tex]

Differentiating with respect to time

           [tex]\frac{dV}{dt}=\frac{4}{3}\pi \times\frac{dr^3}{dt}\\\\\frac{dV}{dt}=4\pi r^2\times\frac{dr}{dt}[/tex]

Given that

            [tex]r=10cm\\\\\frac{dV}{dt}=-8cm^3/hr[/tex]

Substituting

            [tex]\frac{dV}{dt}=4\pi r^2\times\frac{dr}{dt}\\\\-8=4\pi \times 10^2\times\frac{dr}{dt}\\\\\frac{dr}{dt}=-6.37\times 10^{-3}cm/hr[/tex]

The radius of the snowball is decreasing at a rate 6.37 x 10⁻³ cm/hr