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

• Taiki_Kazuma
In summary, the force pushing against a sign attached to a vehicle can be calculated using the formula D=\frac{1}{2}*C_D*r*v^2*A, where A is the area of the sign, v is the velocity of the vehicle, r is the air density, and C_D is the coefficient of drag. After making the necessary conversions, the final force is significantly lower than 9651 lbs.
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

!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.

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!

## 1. What is wind resistance?

Wind resistance, also known as air resistance, is the force that opposes the motion of an object through the air. It is caused by the friction between the object and the air molecules as it moves through the atmosphere.

## 2. How does wind resistance affect objects?

Wind resistance can slow down the movement of objects by exerting a force in the opposite direction of their motion. This can be seen in activities like cycling or running, where the wind can make it more difficult to move forward.

## 3. How is wind resistance calculated?

The calculation of wind resistance depends on various factors, such as the shape and size of the object, the speed of the object, and the density of the air. The most common formula used to calculate wind resistance is the drag equation, which takes into account these variables.

## 4. How can wind resistance be reduced?

There are several ways to reduce wind resistance, such as using a streamlined shape for objects that need to move through the air, like airplanes and cars. Another method is to decrease the surface area of the object, as this will reduce the amount of air molecules that come into contact with it.

## 5. How does wind resistance affect the flight of airplanes?

Wind resistance plays a crucial role in the flight of airplanes. It affects the amount of lift generated by the wings, as well as the amount of drag experienced by the plane. Pilots must take wind resistance into account when planning flights and adjusting their speed and angle of ascent or descent.

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