Lift, Thrust, and Flight

Force is the push or pull that acts on an object. That push or pull could cause the object to change in the speed and/or direc-tion of its motion, including the initation of motion from rest. That push and pull can also cause the object to deform. Force (F) is a vector quantity with both magnitude and direction. When describing a force, one must specify its magnitude, its direction, and its line of action. Motion refers to changes in the location of an object. Motion is always observed and measured relative to a frame of reference. An object that is motionless relative to a given frame of reference could be moving relative to infinitely many other reference frames. Thus, the frame of reference is critical when describing forces and motions. When the speed of an object is much less than the speed of light, Newton’s three laws of motion describe quite accurately the relationship between forces, motions, and the frame of reference. Newton’s three laws of motion are as follows