Verified answer

I think the formula is

F = ½ρAv²C

where ρ = density of fluid. air at about 0.075 lbm/ft³

and A = cross-sectional area = 6.67ft * 2.5ft ≈ 16.7 ft²

and v = velocity = 45 m/s = 148 ft/s

and C = drag coefficient = somewhere between 1 and 2 for a flat plate -- I'll take 2.

At least the units for this formula work out to be Newton's (and ρv² does not).

Then F = ½ * 0.075lbm/ft³ * 16.7ft² * (148ft/s)² * 2 = 27400 lbm·ft/s²

Divide by 32.2 to get to pounds force:

F ≈ 850 lbs

F=p.v2

where p = density of air

using impulse momentum equation, force is independent of area