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In a table fan, the blades move around in circular way and we feel air/wind when sitting on front of it. How does this happen?

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1 Answer 1

up vote 6 down vote accepted

The blades are at an angle. As the blade moves down it hits an air molecule and the air molecule "bounces off" toward you.
It's just like hitting a ball in tennis/baseball

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This suggests a violation of no-slip at the fan edge. It is better to state it in term of air-currents reflecting, rather than atoms, because the atoms are not moving individually. –  Ron Maimon Oct 20 '11 at 6:05
    
If atoms don't move how does a fan distribute a smell accross the room? –  Martin Beckett Oct 20 '11 at 13:00
    
The atoms which are directly in contact with the fan don't move. The atoms which "bounce off" the fan are bouncing off the layer of air stuck to the fan. This is the continuum approximation and it is valid unless you have a shock-wave super-fan. See also this: physics.stackexchange.com/questions/1343/… –  Ron Maimon Oct 21 '11 at 2:11

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