Air Resistance
Air Resistance is a force that acts opposite of an object’s motion due to air. It is also called air friction. The reason it happens is that air is made of particles. The moving object must posh these particles out of the way to get through. The particles each push back a little causing air friction.
Factors Affecting Air Resistance
There are two main factors that affect air resistance
Surface area/Shape
The greater the surface area the more particles of air hit the object. The more particles that hit the greater the friction and force that goes against motion.
More surface area more air resistance
Speed
The faster the object is moving through the air the more particles hit is increasing friction. Also the faster the particles hit the more force which goes against motion.
More speed, more air resistance
Surface area/Shape
The greater the surface area the more particles of air hit the object. The more particles that hit the greater the friction and force that goes against motion.
More surface area more air resistance
Speed
The faster the object is moving through the air the more particles hit is increasing friction. Also the faster the particles hit the more force which goes against motion.
More speed, more air resistance
Example
When riding in a car with your hand out the window: Surface Area: When your hand is facing the ground there is less air resistance. When it is facing forward the air pushes your hand backwards. Speed: At a slow speed you can't feel much of the force of the air resisting you. But at a fast speed it is very strong |
Terminal Velocity
Terminal Velocity is when a falling object travels at a constant speed down with no acceleration. This is because, as something falls through the air, it accelerates (gets faster). As it gets faster it has more air resistance. Eventually, the air resistance increases to a point and stops. At this time the gravity force and the air resisance are equal and opposite and become balanced. When the forces are balance the object does not accelerate (speed up or slow down), but travels at a constant speed.
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Positive and Negative Affects of Air Resistance
Positive Effects
It is positive if used to slow down, like parachutes or air brakes on planes. |
Negative
It is negative if you don't want to waste energy, like cars, bikes, airplanes. These are designed to be streamlined. |