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All of the sources I read says that friction is independent of surface area, but when we throw a heavy object with large area from a certain height, it experiences more air drag, which is related to friction, but when we throw another object of equal mass and smaller surface area, it experiences less drag.

Also, a circular or spherical wheel like structure experiences less friction than a cubical block of equal mass and equal co-efficient of friction.

Can you explain me why it happens?

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marked as duplicate by John Rennie newtonian-mechanics Aug 11 '16 at 5:20

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    $\begingroup$ Your source is talking about one individual object, not a comparison of the friction experienced by two different objects. For a single rectangular object, placing the object on its smallest side, or its largest side, will produce the same friction force when the object is dragged, because friction force is proportional to the object's weight, not how much area of the object is in contact with a "frictional" surface. $\endgroup$ – David White Aug 11 '16 at 4:07
  • $\begingroup$ Friction between solid surfaces is not the same as drag on solid objects passing through fluids such as air, so you can't apply the same rules. A rolling wheel does not experience the same kinetic friction that a sliding block does. Instead, there is static friction that prevents slipping but removes no energy from the wheel, and there can be rolling resistance, which is different. $\endgroup$ – EL_DON Aug 11 '16 at 7:05
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It is because of the surface area which is going to experience the air force the substances which are having more area they experience more force.when you conduct the experiments under constant conditions i.e. in vacuum you will get the result what you expected in this case the area which is exposed to the air pressure matters

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