In mechanics, a force is that which causes a change in velocity or, if you prefer, that which causes an acceleration. When more than one force acts on an object it is the net force that is important. Since force is a vector quantity, use geometry instead of arithmetic when combining forces.
Quick Answer. A crawling sensation felt on the skin may be caused by a condition called morgellons, according to WebMD. Common symptoms of morgellons include feeling like bugs are crawling on the skin, burning, itching and stinging sensations. In some cases skin sores may appear as well.
Skin drag Skin drag is caused by the friction between the surface of the object and the fluid. The skin drag depends mainly on wetted surface of the object. It increases with speed in similar way to the form drag, so for practical purposes it is usually combined with the form drag into one term, the parasitic drag.