Sorry! T is for a pendulum. It should be changed to Normal force \vec{N} for your case.
But the equation is the same.
For you case: \hat{r} is the unit vector from (5,0) to (x,y) of the ball.
i.e. unit vector of (x-5,y) or ( \frac{x-5}{\sqrt{(x-t)^2+y^2}}, \frac{y}{\sqrt{(x-t)^2+y^2}})