why does a fan rotate when you blow on it ?

Question

need to understand the physics about when the wind hits the fan why it rotates

Answer 1

wind simply does the work that ur hands might have done it;
its physics is inlaid in the concept of torque;

torque is defined as the product of foce applied and the perpendicular distance between the of line of action of force and the fulcrum moving point

its like we push or pull a door
a moment of torque is created
the force we apply* the perpendicular distance between our application of force and the hinge of the door or the fulcrum

more the distance=>more will be the torque
more the force=> more will be the torque

this is what the winds do.......the centre of the fan is sort of a fulcrm and the leafs are like oujutting 'doors'
a moment of torque is created by the force of the winds

work done = force* distance moved by the object
the more force the winds apply=> the more the fan will move

hope u understood=>u can always take more help from me

Answer 2

Yep, a diagram would help! :)

A fan or propeller is shaped so that the tip spins faster than the centre (fans have more than two blades). The blades are twisted, steep in the middle, less so at the edge, which allows the thrust to keep it moving. Your blow gives it the initial force. As the fan rotates the blades push the air in one direction and experience a reaction force in the opposite direction as a result. Each experiences a "lift" force, typically called "thrust," in the direction opposite the airflow.

The physics is similar to that of an aerofoil (the shape of a wing). A fan is just like a spinning wing.

“As a wing moves through air, the air is split and passes above and below the wing. The wing’s upper surface is shaped so the air rushing over the top speeds up and stretches out. This decreases the air pressure above the wing. The air flowing below the wing moves in a straighter line, so its speed and air pressure remain the same.
Since high air pressure always moves toward low air pressure, the air below the wing pushes upward toward the air above the wing. The wing is in the middle, and the whole wing is “lifted.” The faster an airplane moves, the more lift there is. And when the force of lift is greater than the force of gravity, the airplane is able to fly.”

Answer 3

If you think about it, what's happening is just the opposite of what happens when you turn the fan on.

With the fan on, it rotates, and the angle of the blades causes air to be blown into the room. When you blow on it, you're causing air to blow in the opposite direction, so the angle of the blades causes the fan to rotate - in the opposite direction to the way it turns when the power is on.

Does that make sense?

Answer 4

Because the blades of the fan arent flat but at an angle.
Wind comes in and deflects off the fan in one direction making the fan blade move in the other. I could explain better with a diagram

Answer 5

Becase of the angle of the blades. The same theory can be applied if you power the fan. The angle of the blades cutting through the air cause a draught.

Answer 6

simply ...the fan blade are not horizontal.....so the vertical force caused by the air blow will have two components ...one is vertical pushing the fan verticaly ....and the other is horzintal moving the fan horizontally causing it to rotate (equal to cos Q, where Q is the angle of the blade bendding)...

Answer 7

A fan is just a glorified version of a kid's pin-wheel or a windmill in reverse. When driven by the motor air is pushed forward. When blown upon (motor off), the blades rotate in the opposite direction.

When a flow of air strikes the angled blades they rotate .. .impulse type turbine


... Air Flow → /___
........................↓ direction of blades

Answer 8

it's all to do with the shape of the blades.

Answer 9

because you are blowing on it