I need quick help for the following question. I got the first part but the bonus question I'm having trouble with.
A 57.0 kg diver dives from a height of 15.0 m. She reaches a speed of 14.0 m/s just before entering the water. What was the average force of air resistance (e.g., friction) acting on the diver?
Bonus: What is the force of friction underwater if she reaches a depth of 2.5 m before stopping? Do not neglect the buoyant force of 500 N acting on the diver once underwater?

Question

I need quick help for the following question. I got the first part but the bonus question I'm having trouble with. 
A 57.0 kg diver dives from a height of 15.0 m. She reaches a speed of 14.0 m/s just before entering the water. What was the average force of air resistance (e.g., friction) acting on the diver?
 Bonus: What is the force of friction underwater if she reaches a depth of 2.5 m before stopping? Do not neglect the buoyant force of 500 N acting on the diver once underwater?

anonymous · Answer

change in kinetic energy + change in potential energy = work done by friction + work done by bouyancy

hence,

$$1/*m*u^2 + mgd = Friction*d + BouyantForce*d$$