An accident at an oil drilling platform is causing a circular oil slick. The slick is 0.07 foot thick, and when the radius of the slick is 110 feet, the radius is increasing at the rate of 0.9 foot per minute. At what rate (in cubic feet per minute) is oil flowing from the site of the accident? (Round your answer to two decimal places.)

Respuesta :

Answer:[tex]43.54 ft^3/min[/tex]

Step-by-step explanation:

Given

Thickness of oil slick=0.07 foot

radius of slick=110 ft

[tex]\frac{\mathrm{d} r}{\mathrm{d} t}=0.9 ft/s[/tex]

Let V be the volume of oil slick

so, [tex]V=0.07\pi \cdot r^2[/tex]

rate of oil flowing is

[tex]\frac{\mathrm{d} V}{\mathrm{d} t}=0.07\times 2\pi \cdot r\frac{\mathrm{d} r}{\mathrm{d} t}[/tex]

[tex]\frac{\mathrm{d} V}{\mathrm{d} t}=0.07\times 2\pi \times 110\times 0.9=43.54 ft^3/min[/tex]

Rate of something is always with respect to other thing. The rate at which the oil is flowing from the site of the accident is [tex]\approx 43.54\: ft^3/min[/tex]

How to calculate the instantaneous rate of growth of a function?

Suppose that a function is defined as;

y = f(x)

Then, suppose that we want to know the instantaneous rate of the growth of the function with respect to the change in x, then its instantaneous rate is given as:

[tex]\dfrac{dy}{dx} = \dfrac{d(f(x))}{dx}[/tex]

The thickness of the slick is 0.07 foot(constant), and the radius of the spread is increasing at 0.09 foot/minute(constant growth).

Let at some time, the radius be of 'r' units, then

Volume of the oil at that time = [tex]\pi r^2 h = \pi r^2 \times 0.07 =0.07\pi r^2 \: \rm ft^3[/tex]

It is known that

[tex]\dfrac{dr}{dt} = 0.9[/tex] (as rate of increment of radius with respect to time is constant value 0.9 foot/minute)

Thus,

[tex]\dfrac{dV}{dt} = \dfrac{d(0.07\pi r^2)}{dt} = 0.07\pi \dfrac{d(r^2)}{dt} = 0.14\pi r\dfrac{dr}{dt}\\\\\dfrac{dV}{dt} = 0.14 \times \pi \times r \times 0.9 = 0.126\pi r \: \rm ft^3/min[/tex] (instantaneous rate of change of volume when radius is r units)

At r = 110, the rate of volume increment is:

[tex]\dfrac{dV}{dt} = 0.126\pi r \: \rm ft^3/min\\\\\dfrac{dV}{dt}|_{r=110} = 0.126 \pi (110) \approx 43.54\: ft^3/min[/tex]

Thus,  the rate at which the oil is flowing from the site of the accident is [tex]\approx 43.54\: ft^3/min[/tex]

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