A rock is dropped from a tree of height 29 m into a lake (depth 4.5 m) below. After entering the water, the rock floats gently down through the water at a constant speed of 1.7 m/s to the bottom of the lake. What is the total elapsed time?

falls 29 m

a = -g = -9.81 m/s^2
v = 0 - 9.81 t
h = 29 +0 - 4.9 t^2
0 = 29 - 4.9 t^2
t = 2.43 seconds in air
in water:
t = 4.5 /1.7 = 2.65 seconds in water
add them