HI, My question as per above. A quick check with Physicsclassroom.com reveals that a (perhaps too simplistic) reason is that more and more air molecules are hitting the body as the body falls through the air. But i am confused. I thought when the body first falls through the air fluid, the number of air molecules hitting the body is proportional to the surface area of contact, which as we all know, is fixed (body shapes dont change right!). I understand that air resistance is a form of drag force, and this drag force is dependant on velocity of the falling body. What i want to know, however, is how we can explain this phenomena in terms of particle theory. Fellow forummers help me please? A high school physics teacher here.