I am trying to get the volume of an object that is made when you revolve a circle around the x-axis.

The circle has a middle of (0, k) and a radius r.

I know the formula for a circle: $y = sqrt{r^2-x^2}$ and the formula for the integral: $int_{a}^{b}{(f(x))^2dx}$

I have changed the formula of the circle to include k by making $r^2 = x^2 + (y-k)^2$

But then I do not know where to go. I have done a lot of trial-and-error, but nothing seems to work.