This increased mass has an inverse effect upon the rock's acceleration. As an object falls through air, it usually encounters some degree of air resistance. Air resistance is the result of collisions of the object's leading surface with air molecules. The actual amount of air resistance encountered by the object is dependent upon a variety of factors. To keep the topic simple, it can be said that the two most common factors which have a direct effect upon the amount of air resistance are the speed of the object and the cross-sectional area of the object .
Increased speeds result in an increased amount of air resistance.
Increased cross-sectional areas result in an increased amount of air resistance. To answer this questions, Newton's second law will be applied to the motion of a falling skydiver. For each case, use the diagrams to determine the net force and acceleration of the skydiver at each instant in time. Then use the pop-up menus to view the answers. The diagrams above illustrate a key principle.