00:01
So let's start by drawing a picture of this situation.
00:04
So we have a cylindrical tank.
00:08
And at the bottom of the tank, we can say y is equal to zero.
00:12
At the top of the tank, we can say y is equal to four meters.
00:16
And then above the top of the tank is another pipe, which is one meter long, and the water is going to come out of there.
00:23
So in this tank, we will take an elemental volume, which is of thickness, d .y.
00:31
And the radius is r.
00:33
So this volume dv would be equal to pi times r squared dy, or that would be equal to, since r is equal to two meters, therefore we can say that the volume of this would be four pi times dy.
00:50
Now the force df, which is needed to lift this volume up, would be equal to the weight of this volume.
00:59
So that would be equal to 4 pi times 9 ,800 which is the weight of 1 meter cube of water.
01:10
So therefore we can say that d f is equal to 339 ,200 and pi times d .y.
01:23
So this needs to be lifted through a distance of y, 4 minus y meters, but then it also needs to be lifted through another one meter...
