Commonly employed units of linear acceleration are the centimeter per second per second, the foot per second per second, and the mile per hour per second.
Any cause which either produces or tends to produce a linear acceleration of the motion of a body is called force. Commonly employed units of force are the dyne, gram weight, and pound weight.
1 pound weight = 454 grams weight
At a place where the acceleration due to gravity is 980 centimeters per second per second
1 gram weight = 980 dynes
Work is the accomplishment of a change in the position of a body against an opposing force. The magnitude of the work is taken to be equal to the product of the force overcome and the projection of the displacement in the line of action of the force.
W = Fx (4)
The commonly employed units of work are the erg (dyne-centimeter), joule (10' ergs), and the foot-pound.
Energy is stored work. The amount of energy possessed by a system of bodies is the amount of work it can do in passing from its present condition to some standard condition.
The kinetic energy of translation of a body of mass m moving with a linear speed v is
W, = amv2 (5)
Energy, being work, is measured in the same units as work. Power is the time-rate of doing work. If a system does an amount of work W in time t by opposing a constant force F