Fluid Dynamics - Calculating air resistance on air 1. The problem statement, all variables and given/known data I'm trying to figure out how much the velocity of wind will decrease by over a given distance. I know the velocity at a point 1cm after it has passed over an object, and i need to determine the velocity at the object. The flow is turbulent and the object is oscillating. 2. Relevant equations I know the formula for air resistance is F=1/2"rho"v^2*C*L^2, where rho is the density, v is the relative velocity, c is the coefficient of drag and L is the length. 3. The attempt at a solution I have no idea what to do when the question concerns air resistance acting on air. I do not know how to treat length in the equation, as I don't understand how air can have a length. I also do not understand how to find the coefficient of drag on air.