Answer:
6.89 m
Step-by-step explanation:
t = Time taken
u = Initial velocity
v = Final velocity
s = Displacement
a = Acceleration

The water balloon will take 2.9 seconds to hit the tree
As, the truck is moving at a constant speed of 20 m/s it does not have acceleration

The boy has to release the balloon when the truck is 6.89 m away