Force
In physics, a force is any interaction that, when unopposed, will change the motion of an object. A force can cause an object with mass to change its velocity (which includes to begin moving from a state of rest), i.e., to accelerate. Force can also be described intuitively as a push or a pull. A force has both magnitude and direction, making it a vector quantity. It is measured in the SI unit of newtons and represented by the symbol F.
English Engineering units
In English Engineering units, the pound mass and the pound force are distinct base units, and Newton's Second Law of Motion takes the form "F" = "ma"/"g", where "g" = 32.174 lb·ft/(lbf·s).