A spherical snowball is melting in such a way that its radius is decreasing at a rate of 0.4 cm/min. At what rate is the volume of the snowball decreasing when the radius is 15 cm. (Note the answer is a positive number).

Respuesta :

Answer:

1130.97 cm/min.

Step-by-step explanation:

The volume of a sphere is given by the following equation:

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

We have to do the implicit differentitaiton of V in function of t. The are only two variables(V and r). So

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

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

We have to find [tex]\frac{dV}{dt}[/tex] when [tex]\frac{dr}{dt} = -0.4, r = 15[/tex]. So

[tex]\frac{dV}{dt} = 4\pi*(15)^{2}*(-0.4)[/tex]

[tex]\frac{dV}{dt} = -1130.97[/tex]

The negative means that the volume is decreasing.

The volume of the snowball is decreasing at the rate of 1130.97 cm/min when the radius is 15 cm.

So the answer is 1130.97 cm/min.

When the radius is 15 cm, the volume will decrease at a rate of -1,130.4 cm^3/min

At what rate the volume of the snowball is decreasing?

We know that for a sphere of radius R, the volume is:

V = (4/3)*3.14*R^3

The radius decreases at a rate of 0.4 cm/min, and we want to find the rate when the radius is 15cm, then we can write:

R = 15cm - (0.4 cm/min)*t

Then the volume will be:

V(t) = (4/3)*3.14*(15cm - (0.4 cm/min)*t)^3

To get the rate of change, we need to differentiate with respect to t, we will get:

V'(t) = 3*(4/3)*3.14*(15cm - (0.4 cm/min)*t)^2*(-0.4 cm/min)

The rate of change when the radius is 15 cm, is V'(0), so we get:

V'(0min) = 3*(4/3)*3.14*(15cm - (0.4 cm/min)*0min)^2*(-0.4 cm/min)

V'(0min)= 3*(4/3)*3.14*(15cm)^2*(-0.4 cm/min) = -1,130.4 cm^3/min

If you want to learn more about rates of change, you can read:

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