Answer:
Below
Step-by-step explanation:
The stone has an initial velocity, vo, = to upward velocity of the balloon.
displacement = do + vo t + 1/2 a t^2 do = 171 m a = - 9.81 m/s^2
t = 9 displacement = 0 when it hits the ground
0 = 171 + vo ( 9) - 1/2 (9.81)(9^2)
v o = 25.145 = ~ 25 m/s