for moving objects, the quantity of work/time (power) is integrated along the trajectory of the point of application of the force. thus, at any instant, the rate of the work done by a force (measured in joules/second, or watts) is the scalar product of the force (a vector), and the velocity vector of the point of application. this scalar product of force and velocity is known as instantaneous power. just as velocities may be integrated over time to obtain a total distance, by the fundamental theorem of calculus, the total work along a path is similarly the time-integral of instantaneous power applied along the trajectory of the point of application.