Work is defined to be the product of force over the distance it is applied. In symbols, , where is the work, is the force, and is the distance.
Power, , is work per unit time, so , where is time.
This Demonstration calculates the work and power needed to lift a mass through a height in time . The darkness of the blue box indicates its mass. The distance is fixed to be and , the standard SI measurement for gravity. In this situation, Newton's second law, , where is acceleration, becomes . Substituting for in the first equation gives .