what is air resistance?

Answer 1

As an object falls through air, it usually encounters some degree of air resistance. Air resistance is the result of collisions of the object's leading surface with air molecules. The actual amount of air resistance encountered by the object is dependent upon a variety of factors. To keep the topic simple, it can be said that the two most common factors which have a direct effect upon the amount of air resistance are the speed of the object and the cross-sectional area of the object. Increased speeds result in an increased amount of air resistance. Increased cross-sectional areas result in an increased amount of air resistance.

Answer 2

Air is a substance, remember that. When you say a bottle is "empty", it is actually not. It is full of air.

Have you ever tried running in the sea? You can't. Why? Because you get a lot of resistance. Now water is a much more dense substance than air. The molecules (or just say the particles it is made of) are closer to each other, hence you get a lot of them hitting you. In air they are further away from each other, and you don't feel it that obviously, but speed has a very huge effect on resistance. If it was not a dangerous move, I'd say stick your hand out of a car doing 60MPH. You'll feel that the air also has resistance.

Have you ever felt like no matter in which direction you were riding the bike, you always had head wind? That is air resistance pushing you back. The faster you ride, the stronger you feel the "wind".

In fact, it increases with the square of the speed. If you double the speed, the resistance (or drag) becomes 2x2=4 times as much. If you triple the speed, your resistance becomes 3x3=9 times as much.

Answer 3

Is a force opposite of the object in motion, just like friction.

Although on earth all things fall at the same time despite different masses on a vacuum, these thing fall differently due to resistance.

Example:
On a vacuum (no air or other matter), a feather a rock would fall at the same time, but on earth, the feather would appear flying and slow falling, this is due to the air that pushes the movement of the feather upwards, interfering with its downfall.

Try searching the internet for answers.

Answer 4

Atkinson resistance is commonly used in mine ventilation to characterise the resistance to airflow of a duct of irregular size and shape, such as a mine roadway. It has the symbol R and is used in the square law for pressure drop,


where (in Imperial units)

ΔP is pressure drop (pounds per square foot),
ρactual is the air density in the duct (pounds per cubic foot),
ρref is the standard air density (0.075 pound per cubic foot),
R is the resistance (atkinsons),
Q is the rate of flow of air (thousands of cubic feet per second).
One atkinson is defined as the resistance of an airway which, when air flows along it at a rate of 1,000 cubic feet per second, causes a pressure drop of one pound per square foot.

The unit is named after J J Atkinson, who published one of the earliest comprehensive mathematical treatment of mine ventilation. Atkinson based his expressions for airflow resistance on the more general work of Chézy and Darcy who defined frictional pressure drop as


where

ΔP is pressure drop,
ρ is the density of the fluid in question (water, air, oil etc.),
f is the Fanning friction factor,
L is the length of the duct,
S is the perimeter of the duct,
A is the area of the duct,
v is the velocity of the fluid.
The practicalities of mine ventilation led Atkinson to group some of these variables into one all-encompassing term:

Area and perimeter were incorporated because mine airways are of irregular shape, and both vary along the length of an airway.
velocity v was replaced by the ratio of flowrate to area (Q / A) because variations in area cause variations in velocity. Area was then incorporated into the denominator of the Atkinson resistance term.
Length of the airway was incorporated. This may have been a step too far, as most of his successors chose to give values of Atkinson resistance in terms of atkinsons per unit length (often 100 or 1000 yards).
The term 1 / 2ρ was incorporated, which later authors definitely considered a step too far (e.g. McPherson, 1988). In fairness, in Atkinson's time not only were all British mines shallow enough that the density of air could be considered constant, but fan design was primitive enough that variations in density would make no measurable difference to the amount of motive power required. Atkinson did not foresee that his methods would be applied several miles underground, where air is 30–50% denser than it is at the surface. Density variations of this magnitude can alter the power consumption of colliery ventilation fans by hundreds of kilowatts.
The resulting term is one that can be easily calculated from the results of two simple measurements: a pressure survey by the gauge and tube method and a flowrate survey with a counting anemometer. This is a major strength and is the reason why Atkinson resistance remains in use today.

A complete definition of Atkinson resistance R in more common fluid flow terms is as follows:

Answer 5

Air resistance (′er ri′zis·təns)

(mechanics) Wind drag giving rise to forces and wear on buildings and other structures.

Answer 6

got an air compresser?,,, hold your hand in front of an air gun,,, move your hand closer and away from the gun while its blowing,,, be careful, the closer you get to the tip, it can burn you like fire,,, its friction,,, resistance