physics
posted by Nick .
A lead ball is dropped into a lake from a diving board 5.24 m above the water. It hits the water with a certain velocity and then sinks to the bottom with this same constant velocity. It reaches the bottom 4.86 s after it is dropped. (Assume the positive direction is upward.)
(a) How deep is the lake?
(b) What is the average velocity of the ball?
(c) Suppose that all the water is drained from the lake. The ball is now thrown from the diving board so that it again reaches the bottom in 4.86 s. What is the initial velocity of the ball?

On the first, calculate the time it takes for something to drop 5.24m, then subtract that time from the total time. depth lake=vf*time
You can calculate vf from vf^2=2g h
and calculate time to surface..5.24=1/2gt^2