Kinetic and Potential Energy related problem - need help please!!!?

Question

A 71.0 kg diver steps off a diving board and drops straight down into the water. The net force when in the water is an upward 1440 N. If the diver comes to rest 4.7 m below the water's surface, what is the total distance between the diving board and the diver's stopping point underwater?

(answer in meters)

Answer 1

First solve the second part of the problem (that is, the motion that occurs in the water)

2 a d = v^2 - vo^2

a is the acceleration (unknown)
d is the distance traveled (4.7 m)
v is the final velocity (zero)
vo is the initial velocity (unknown)

To get the acceleration, use net force = ma

1440 N - mg = ma

Solve for a, then use the equation above to solve for vo. This velocity, the starting velocity for the second half of the problem, will be the final velocity for the first half.

Now we can tackle the initial part of the problem, using the same equation:

2 a d = v^2 - vo^2

a is the accelation, 9.8 m/s^2 down
d is the distance (unknown)
v is the final velocity (the value of vo from the previous part)
vo is the initial velocity (zero)

Solve for d