A line segment begins at $(2, 5)$. It is 10 units long and ends at the point $(-6, y)$ where $y > 0$. What is the value of $y$?
We use the distance formula: \begin{align*}
\sqrt{(2 - (-6))^2 + (y - 5)^2} &= \sqrt{8^2 + (y - 5)^2} \\
& = \sqrt{y^2 - 10y + 89} \\
& = 10.
\end{align*}Squaring both sides and rearranging terms, we find that \begin{align*}
y^2 - 10y + 89 &= 100 \\
y^2 - 10y - 11 &= 0\\
(y - 11)(y + 1) &= 0
\end{align*}Thus, $y = 11$ or $y = -1$. We are given that $y > 0$, so $y = \boxed{11}$.