A diver of mass 60 kg, on entering water with an initial velocity of 15.35 ms^{-1, }experiences a force of resistance, due to the water opposing motion, of magnitude 180v Newtons, where v is the velocity of the diver in ms^{-1}. In addition to the force of gravity, the diver also experiences a constant upward buoyancy force of 720 N. Take the origin of motion to be at the surface of the water. The magnitude g of the acceleration due to gravity can be taken as 10 ms^{-1. }

Calculate the maximum depth, in metres, the diver will submerge. Give your answer to 3 decimal places.

The answer is 4.41. I cant get it no matter how i try. Hopefully someone could enlighten me

From what i know Fnet= 720+180v-mg and that Fnet=ma

Therefore, i got a=2+3v after simplifying. From there i'm stuck because from what i noticed, acceleration is not constant, so the uniform acceleration/deceleration formula could not be applied.