How Much Force Does Wind Resistance Exert on a Vehicle-Mounted Sign?

[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

 

[member 553083]

!The air density and coefficient of drag are correct, but it looks like you may have converted the velocity incorrectly. 80 mph is equivalent to 35.76 \frac{m}{s}, not \frac{m}{s^2}. So your final answer should be a lot lower than 9651 lbs.

 

[thepatientmental]

First of all, great job on setting up the equation and calculating the force! It seems like you have all the correct values and calculations, so your answer of 42929 N or 9651 lbs should be correct. Wind resistance is definitely a significant force to consider when attaching a sign to a vehicle, and your calculations show just how much force can be exerted. Keep in mind that these calculations are based on ideal conditions and may vary in real-life situations. Overall, your approach and calculations seem correct and thorough. Great work!