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Elan Coil [88]
3 years ago
6

) The density of oil in a circular oil slick on the surface of the ocean at a distance of r meters from the center of the slick

is given by δ(r)=401+r2 kilograms per square meter. Find the exact value of the mass of the oil slick if the slick extends from r=0 to r=5 meters.
Mathematics
1 answer:
Feliz [49]3 years ago
3 0

Answer:

Therefore the mass of the of the oil is 409.59 kg.

Step-by-step explanation:

Let us consider a circular disk. The inner radius of the disk be r and the outer diameter of the disk be (r+Δr).

The area of the disk

=The area of the outer circle - The area of the inner circle

= \pi (r+\triangle r)^2- \pi r^2

=\pi [r^2+2r\triangle r+(\triangle r)^2-r^2]

=\pi [2r\triangle r+(\triangle r)^2]

Since (Δr)² is very small, So it is ignorable.

∴A=2\pi r\triangle r

The density \delta (r)= \frac{40}{1+r^2}

We know,

Mass= Area× density

        =(2r \pi \triangle r)(\frac{40}{1+r^2}})

Total mass M=\sum_{i=1}^n \frac{80r_i\pi }{1+r^2}\triangle r_i

Therefore

\sum_{i=1}^n \frac{80r_i\pi }{1+r^2}\triangle r_i=\int_0^5 \frac{80r\pi }{1+r^2}dr

                      =40\pi[ln(1+r^2)]_0^5

                      =40\pi [ln(1+5^2)-ln(1+0^2)]

                     =40\pi ln(26)

                     = 409.59 kg (approx)

Therefore the mass of the of the oil is 409.59 kg.

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