The stone in a balloon with the mass of $m$ is falling from the height of $H$. Find the velocity of this stone. (Ignore the mass of balloon and air resistance).
I found the answer as
$$\sqrt {\frac{v^2_{s}+2Hg + v_{b}}{g}}$$
where $v^2_{s} = $velocity of stone, $v_{b} = $ velocity of balloon, $g = $ gravitational acceleration.
If this stone wasn't in a balloon, then we could do
$$\frac{1}{2}mv^2 = mgh$$
Am I right?