As in previous analysis, the main key of this point is to analyze the circle, this looks as follows
the tip of the blade is located over the circle. We are interested on the y-coordinate of the tip of the blade. So, imagine that there is some angle between the initial position and the actual position at any time
Then, in this case, the position of the tip of the blade is determined as

where r is the radius of the circle. In this case, r=10. So the expression would be

So, in this case, the y-coordinate would be

this analysis assumes that the center of the circle is at height 0. Since the center of the circle is at height 38, then if we add 38 m we would get the expression of the tip of the blade. So we get

Now, we have to find the expression for theta at any time. The key is to use the rate as the blade rotates, and multiply it by the time. As an examples, suppose that 3 seconds have passed. So the angle would be

So, in general, after t seconds, the angle would be

So we replace this expression for theta

Now, we want to find how much time has passed so the height is 40. So we make this expression equal to 40.

Then, we subtract 38 on both sides, so we get

Now, we divide both sides by 10, so we get

Now, we apply the inverse sine function. So we get

Now, we multiply both sides by 3 and divide it by 2, so we get

So after 0.30203 the height is 40 meters.