Distance a bullet will travel while shot underwater

[Wanna_be_Feynman]

Homework Statement

hey

I am trying to work out the problem:
If I shoot an ak47 underwater with 7.62x39mm ammunition, how far will the bullet travel before coming to a stop?

Homework Equations

The equation that I have used to find the drag force is the drag equation:

F =1/2 p*A*C_d*v^2

where:
p is the density of the water (1000 kg/m^3)
v is the velocity of the bullet (730 m/s)
A is the cross sectional area of the bullet with diameter 7.62mm
C_d is the drag coefficient to which I am using 0.29 based from a website which had statistics about the bullet

The Attempt at a Solution

I have found this I get approximately 850, 000 N of force. I am then stuck as to how to calculate the distance the bullet travels before it stops.

 

[PeroK]

The Attempt at a Solution

I have found this I get approximately 850, 000 N of force. I am then stuck as to how to calculate the distance the bullet travels before it stops.

Because the drag force varies with velocity, you will get a differential equation in $v$. The drag force will not be constant. The first step is to derive this differential equation.