A cylindrical water tank 6 meters high with a radius of 2 meters is buried so that the top of the tank is 1 meter below ground level. How much work is done in pumping a full tank of water up to ground level? (The water weighs 9800 newtons per cubic meter.)

Respuesta :

Answer:

W=96040π N*m

Explanation:

Weight water is [tex]=9800 N/m^3[/tex]

Weight layer is [tex]9800*v N/m^3[/tex]

The v is given by

[tex]r=2m[/tex]

[tex]v=\pi*r^2*y' =(4\pi*y')m^3[/tex]

so weight layer is

[tex]9800*4\pi*y'=39200\pi[/tex]

The distance layer moved is

[tex]d=7-y[/tex]

So the work is

[tex]W=\int\limits^7_0{(7-y)*39200\pi } \, dy[/tex]

[tex]W=39200*[7*y-\frac{y^2}{2}] |0,7[/tex]

[tex]W=39200*[49-24.5]=39200\pi *24.5[/tex]

[tex]W=960400\pi N*m[/tex]

The required work done is [tex]940800\pi[/tex]

Given,

Radius=2m

Height=6m

As the tank is below the ground level by 1m

The center of the mass of the water is,

[tex]H=\frac{6}{2}+1\\=4 m[/tex]

The formula of the volume of the cyllindrical tank is,

[tex]V=\pi r^2h[/tex]

Now, substitute the given values into the above formula we get,

[tex]V=\pi r^2h\\=\pi(2)^2\times6\\=24\pi m^3[/tex]

The given density is 9800[tex]N/m^3[/tex]

[tex]weight=density \times volume\\=9800\times24\pi\\=235200\pi N[/tex]

So, the required work done is,

[tex]Work=mgh\\=235200\pi \times4\\=940800 \pi[/tex]

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