How fast is the balloon moving when it is halfway down the building (assume no friction)?
So the question is how fast when it drops 22 meters?
s = (1/2)at^2 where a is assumed to be 9.81 m/s^2
That poses a new question: How much time to fall 22 meters?
d = at
t = d/a = 22/9.81 =2.2426 s
s = 9.81/2 x 5.02929 = 24.6687 m/s
When assembling your equation you need to remember that the units have to cancel same as any other fraction.
s (meters/sec) = (1/2) x (9.81 m/sec^2) x (t sec)^2 That does not make sense because seconds cancel totally and there is no /sec in the answer. So I have misremembered the equation. (At my age that happens a lot.) Do it again:
s = (1/2) at = 9.81/2 x 2.2426 = 11 m/s Now the units come out right.