Killer whales at Sea Worl routinely jump 8 m above the water. What is their speed as they leave the water to achieve this?

Question

I know that h=8m
v=?

Would I use h=h_0 + v_0t = 1/2 at^2
but the problem would be that I also don't know the time. I am confused about which equation best suits this question.

Answer 1

vf^2=vi^2+2gh
vf=0

vi= sqrt (2gh)