00:01
So in this question, we have a square laminar with vertices.
00:05
So we've got x and y.
00:06
We've got vertices 0 -0, 1 -0.
00:14
We've got 1 -1, and we've got 0 -1.
00:20
So this is our laminar.
00:27
That's our laminar.
00:29
And the density is proportional to the square of the distance from the origin.
00:34
So that's x -square plus y squared.
00:38
So now we want to find the mass.
00:41
Well the mass is going to be the integral dx, d .y, from 0 to 1 in both cases of the density, which is row nought x squared plus y squared.
00:55
So let's do the y integral first.
00:59
So this is the integral from 0 to 1 d x.
01:01
We can pull out the row nought, and we get x squared y plus 1 third y cubed between y equals 0 and y equals 1.
01:10
So y equals 0 we don't get anything.
01:12
For y equals 1 we get x squared plus a third.
01:20
So now we can integrate that.
01:24
So that's going to give us x cubed over 3 plus x over 3 between 0 and 1...