posted by Daddee on .
When a stone is thrown into the air it's surface will be in contact with the surrounding air. Analyse the stresses existing between the stone and the surrounding air.
The collisions of the stone with air molecules tend to slow the stone down slightly. A frictional force called drag is exerted upon the stone. It is of two types: (1) pressure drag (higher pressure in front that behind) and (2) boundary layer friction along the sides.