With what speed does the water balloon hit the ground?

Question

Thrown 15.8m above the ground. With what speed does the water balloon hit the ground? How long does it take?

Answer 1

Energy conservation.
Let the water balloon mass to be m. The potential energy is:
mgh = m*9.81*15.8 = 155m
"Thrown" is not a good word here, since it means that the initial velocity is not zero, and you failed to specify the initial velocity. Let us assume that the water balloon is "dropped"
Let the final speed to be V, with which the water balloon hits the ground. We have the kinetic energy converted from the potential energy;
0.5*m*V^2 = 155m
or V = sqrt(2*155) = 17.6 (m/s)
Time taken = V/g = 17.6/9.81 = 1.79 (s)