Energy, Grabity and Calculating Net Force of a Diver

[copitlory8]

Homework Statement

A 60.0-kg person, standing on a diving board, dives straight down into the water. Just before striking the water, her speed is 6.50 m/s. At a time of 1.75 s after entering the water, her speed is reduced to 1.10 m/s. What is the average net force (magnitude and direction) that acts on her when she is in the water?

Homework Equations

F=ma
Kinematics Equations
V=d/t

The Attempt at a Solution

I multiplied the mass times gravity (9.8) and get the downward force. I used 6.5 as the initial velocity and 1.1 as final velocity. Then deacceleration can be calculated. But i don't know where to go from here.

 

[kuruman]

You know the acceleration as she goes through the water and you know her mass. Can you find the net force acting on her from this information?