A high diver jumping off a board (basic force problem)

[AsuraSky]

Homework Statement

A high diver of mass 50.0 kg jumps off a board 10.0 m above the water. If her downward motion is stopped 2.30 s after she enters the water, what average force did the water exert on her?

Homework Equations

F_net=ma
v_f²=v₀²+2ax

The Attempt at a Solution

First I found the final velocity of the diver when she hits the water

v_f²=0²+2(9.8)(10)=196

v_f=14 m/s

Since she is slowed to a stop in 2.3s the average acceleration would be

14/2.3 = 6.08696

Knowing acceleration and her mass, we can calculate the force.

F=50(6.08696)=304.348

This answer was marked wrong. I'm pretty sure I did everything right. Am I missing something?

 

[kuruman]

Your calculation is correct for the magnitude of the acceleration. Maybe the dumb machine that marked this problem expected a negative sign in front of the acceleration. I say "dumb" because the acceleration is in the "up" direction which is conventionally positive. You may have to ask your teacher for a clarification of this point.

 

[AsuraSky]

Thanks for your input, I'll be sure to ask my professor about this problem.