The work W done by a constant force acting on an object is where F is the magnitude of the force, s is the magnitude of the displacement, and θ is the angle between the force and the displacement vectors. Work is a scalar quantity and can be positive or negative, depending on whether the force has a component that points, respectively, in the same direction as the displacement or in the opposite direction. The work is zero if the force is perpendicular = 90 ° to the displacement. The kinetic energy KE of an object of mass m and speed v is The work– energy theorem states that the work W done by the net external force acting on an object equals the difference between the object's final kinetic energy KE f and initial kinetic energy KE0 : W = KE f- KE0 . If the net force does positive work, the kinetic energy increases; if the net force does negative work, the kinetic energy decreases. The
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This note was uploaded on 04/09/2008 for the course PHYS 101 taught by Professor Sharp during the Spring '08 term at Ohio State.