The term acceleration, used in physics, is a vector quantity. This means that acceleration contains both a number which is called its magnitude and a specific direction. An object is said to be accelerating if its rate of change of velocity is increasing or decreasing over a period of time and/or if its direction of motion is changing. The units for acceleration include a distance unit and two time units. Examples are m/s² and mi/hr/s. Sir Isaac Newton in his Second Law of Motion defined acceleration as the ratio of an unbalanced force acting on an object to the mass of the object.

The study of motion by Galileo Galilei (1564-1642) in the late sixteenth and early seventeenth centuries and by Sir Isaac Newton (1642-1727) in the mid-seventeenth century was one of the major cornerstones of modern Western experimental science. Over a period of...