How Air Molecules Cause Friction?
Name: Rebecca G.
How do molecules in the air cause air resistance?
Basically, the air molecules just get in the way. Imagine walking through a
crowded room. You have to push people aside or wait for them to move out of
your way. You are forced to move very slowly. Now imagine moving through an
empty room. You can just walk straight where you want to go. When an
airplane or car or ball moves through the air, the air molecules get in the
way, and have to be moved aside -- like moving through a crowded room. Just
like it takes some energy (some force) to move the people aside, the air
molecules also take a force to be moved aside. This is the air resistance
I hope this helps,
For an object to pass through air in any direction (running, falling,
flying ...), the object must push the air molecules out of the way.
There is always some push from the air, called air pressure. This is
what astronauts have to worry about when in space. This is why they
have pressure suits. When moving air molecules out of the way, the
object pushes harder than usual. When the object pushes harder on the
molecules, the molecules push back harder. This extra push from the air
molecules is air pressure. The faster the object moves, the faster it
must push air molecules out of the way. This is why air pressure gets
stronger when an object moves faster through the air.
Dr. Ken Mellendorf
Illinois Central College
Dear Rebecca G.,
An object, say a baseball, travelling through the air will, of course,
collide with all the molecules in its path. Each molecule will be pushed
forward by the collision and so will exert a backward force on the baseball.
Since each molecule is so tiny and so light each collision exerts a very
small force on the baseball, but since there are so many molecules the
combined effect can cause an appreciable amount of air resistance.
Best, Dick Plano, Professor of Physics emeritus, Rutgers University
Air is a mixture, mostly of nitrogen and oxygen molecules. These molecules
"get in the way" of an object trying to move through the air. To move through
the air, the object has to "push" the air out of the way. The molecules "push
back". You can think of this like a person trying to "push" through a crowd. In
order to move forward, the person has to move the "crowd" out of the way. The
more people in the crowd, the more resistance there is for the person to move
through the crowd. While not an exact example, it does describe the basic idea
of the resistance of the movement of the molecule trying to move through the
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Update: June 2012