DISPLACEMENT The change in position of an object. ∆x = xf - xi VELOCITY The rate of change of displacement. AVERAGE VELOCITY Total displacement divided by the time during which displacement occurred. (Greek Delta) A symbol used in physics to denote a change in a quantity. ACCELERATION The rate of change of velocity. AVERAGE ACCELERATION Change in velocity divided by the time during which velocity change occurred. FREE FALL Motion of an object falling with a constant acceleration due to gravity alone. KINEMATICS The branch of physics that deals with the characteristics of motion. SCALAR A quantity that has only a magnitude and no direction. VECTOR A quantity that has both a magnitude and a direction.