Wind Resistance Question

1. Apr 20, 2005

Taiki_Kazuma

Okay, so here's the thing...

$$D=\frac{1}{2}*C_D*r*v^2*A$$

I need to find the Force pushing against a sign that is attached to a vehicle.

The area (A) of the sign is 60"X28" which is 42.672 $$m^2$$

The velocity (v) that the vehicle will be moving is roughly 80 miles per hour which converts to 35.7632 $$\frac{m}{s}$$

The next 2 I'm not sure about....

Air density (r) is 1.229 $$\frac{Kg}{m^3}$$?
and
$$C_D$$ (Coefficeitn of friction) of this sign (which the broad side will be hitting the wind head on) is 1.28?

So I did all this calculation and got

42929 N which is 9651 lbs. That is a hell of a lot of force. I was wondering if I did all this correct...please let me know. Thanks