Is there a law that explains the rotation of the fan and the direction of the air?
552666
For a simple answer look up how a plane propeller works.
452210
Egads.  It's been quite awhile.  I remember some papers at SIGGRAPH a decade or so ago on this topic.\n\nAlright, here's a stab at the explanation.\n\nWith Euler mechanics or Euler angles, there are three reference angles: yaw, pitch, and roll. It is possible to rotate an object using these three reference angles such that two line up causing the inability to do an arbitrary rotation.  Say you roll to the right 90 degrees and this lines up the yaw axis with your pitch axis -- gimble lock results.\n\nWith quaternions, you don't have three reference angles.  You have only one plane and an arbitrary axis of rotation.  Each move creates a new plane and axis of rotation.  As such, there are no additional axes of rotation with which to collide because there is only one axis of rotation and it's position is arbitrary where as with Euler angles, the reference angles are fixed.\n\nI don't know if I've done it justice, but maybe this explanation and the references below will help you stitch together an understanding.
136940
Evaporative humidifier. A fan blows air through a moistened filter or wick, increasing the humidity in the air.
397146
A combination of two factors. Very basic answer here:\n\n\nNewtons' third law: for every action thee is an equal and opposite reaction. (air hitting the bottom of a wing forces the wing upward)\n\nBernoulli’s Principal: As the velocity of air increases, its pressure decreases. Wings are shaped as that the air travels faster over the wing creating a low pressure area. This area of low pressure over the wing 'sucks' the wing upward.
97237
Coriollis force theory indeed\n\n\nCounter clockwise winds travel around a LOW pressure area,upward.. Winds around a High pressure area travel clockwise downward in the Northern hemisphere.....
1158724
the fan will have negligible effect, unless it can cause significant turnover in the room.  Assuming it does, the location of the fan dictates its effect.  At the top of the door, a fan would pull warm air and cycle in cool air near the floor.  The opposite would occur if placed on the floor.
1011862
What does the fan do? Make the air move to cool down hot skin?
596792
Jet engines work on Newton's 3rd law. Throw sometihng back with a certain force and you will be propelled by that same force.\n\nNow, by continuity eqn, Av = A'v'\n\nIf you throw something out of a small area at a high velocity, the rate of flow in the opposite direction is then proportional.
1096144
put a fan in...the temp rises when the air doesn't circulate properly.
900569
No, air pressure is applied in all directions. Down, as well as up. The downward air pressure is negated by the equal upwards pressure.
1087751
The amount of air is the difference in volumes.\nA = V(r+1) - V(r) = (4/3)pi (r+1)^3 - (4/3)pi r^3\nA = (4/3)pi((r+1)^3 - r^3)
690292
The direction of rotation is the direction you look in when you see clockwise rotation. It's the same as the positive axis of rotation, sometimes called the spin axis. (It's also the direction a right-handed screw moves in when turned clockwise.) It may initially be hard to imagine rotation as having a direction like this, but consider the inconsistency that arises when you think of it as being in the tangential (rolling) direction as you do now. What distinguishes the motion of the bottom of the wheel from the top, front or back? These all point in different directions, and there is really no reason that one should be any more of an indicator than another. It's as if rolling it on the ground is somehow a higher "priority" than on the ceiling. These directions, and the direction the wheel rolls in, all actually indicate translational (nonrotary) motions that result from rotation, not rotation itself.
240419
It should flow counterclockwise because of the Coriolis effect.\n\nHowever:\n\n>> But, the Coriolis force is very small, indeed. \n \nCompared to the rotations that one usually sees (tires on a travelling automobile, a compact disc playing music, or a draining sink), the rotation of the Earth is very small: only one rotation per day. The water in a sink might make a rotation in a few seconds and so have a rotation rate ten thousand times higher than that of the Earth. It should not be surprising, therefore, to learn that the Coriolis force is orders of magnitude smaller than any of the forces involved in these everyday spinning things. The Coriolis force is so small, that it plays no role in determining the direction of rotation of a draining sink anymore than it does the direction of a spinning CD. \n\nThe direction of rotation of a draining sink is determined by the way it was filled, or by vortices introduced while washing. The magnitude of these rotations may be small, but they are nevertheless gargantuan by comparison to the rotation of the Earth. I decided to include a picture of a draining sink, and the first one I tried in my house was found to drain clockwise (the opposite of what the silly assertions would have it do here in the northern hemisphere). This direction was determined entirely by the way the tap filled the sink. The direction of rotation of a draining toilet is determined by the way the water just under the rim is squirted into the bowl when it is flushed.<<\n\nI guess you'll just have to observe - I have made the water in kitchen sinks swirl the "wrong" way just for the heck of it, and it doesn't begin to immediately go the "right" way unless I act on it.
572689
No easily measurable effect. There is a small Coriolis effect when flying north or south, but not when flying east or west. The air and Earth are all rotating as a unit, so except for wind, it is no different than driving on the ground. Wind speed and direction is controlled more by heating from the Sun than anything else, and it can blow in any direction. True, prevailing winds to tend to make for quicker travel in one direction, but that is not what you are talking about I think.
373244
clockwise in the northern hemisphere, anticlockwise in the southern. this according to the coriolis force, but of course there otehr factors that might influence the direction of the water (geometry of the sink, external vibrations, you turning your finger in water....)
527581
Expansion coefficients for air can be determined using the attached link.\n\nBest wishes !
361693
Nope.  A vacuum (not "vacume") means that there's not any air to begin with, and because a fan cannot produce air, only move it around, no air will be given off.