Wind Resistance and/or Wind Accumulative Value

[Nighthawk1]

Homework Statement

I'm working on a project and my physics is a bit weak as I haven't done physics since High School and I needed to figure out wind resistance when traveling in a car at various speeds. For example: If you are traveling down the Interstate at 65mph, how much wind resistance will you incur? And let's say that the current natural wind velocity in either direction is zero. For a better example: Let's say I have a hollowed cylinder mounted on the hood of my car and I am traveling at 65 mph. How much wind velocity will go through that cylinder? And let's say the cylinder's interior diameter is 5 inches.

Homework Equations

The Attempt at a Solution

 

[Carid]

Wind resistance will depend a lot on the shape and size of your car. A Hummer H2 and a Porsche G2 will experience rather different amount of resistance.

As for that cylinder, if the shape presents some resistance to the flow of air (which it will) then the air which does manage to get inside will be at a lower pressure but a higher velocity. This is described in http://en.wikipedia.org/wiki/Bernoulli's_principle

Now why would someone want to put an open cylinder on his car hood?

 

[thomate1]

I understand that wind resistance is the force that opposes the motion of an object through the air. It is caused by the collision of air molecules with the surface of the object. The amount of wind resistance experienced by an object depends on its shape, speed, and the density of the air. In the case of a car traveling at 65mph, the wind resistance will depend on the shape and size of the car, as well as the speed and density of the air.

To calculate the wind resistance, we can use the equation F = 0.5 * ρ * A * v^2, where F is the wind resistance force, ρ is the density of air, A is the frontal area of the car, and v is the speed of the car.

In the given example, we can assume that the natural wind velocity is zero, so the only source of wind resistance will be the motion of the car. For a hollowed cylinder mounted on the hood of the car, the wind resistance will depend on the size and shape of the cylinder, as well as the speed and density of the air.

To calculate the wind velocity that will go through the cylinder, we can use the equation v = Q/A, where v is the wind velocity, Q is the volumetric flow rate of air, and A is the cross-sectional area of the cylinder.

In this case, the cross-sectional area of the cylinder is given as 5 inches, which is equivalent to 0.0104 square meters. The volumetric flow rate of air will depend on the density of the air and the speed of the car. Assuming a density of 1.2 kg/m^3 for air, the volumetric flow rate can be calculated using the equation Q = ρ * A * v, where v is the speed of the car.

Therefore, the wind velocity that will go through the cylinder can be calculated as v = (1.2 kg/m^3) * (0.0104 m^2) * (65 mph) = 0.811 m/s.

In conclusion, wind resistance and wind velocity are important factors to consider when designing vehicles and structures that will be exposed to wind. Understanding these concepts can help us make informed decisions and optimize the design for better performance.