Work, Power and Energy

In physics, work is done when a force moves an object through a distance, and it is defined as the force multiplied by the displacement in the direction of that force. Work is the means by which energy is transferred from one object or form to another. Energy itself is the capacity to do work, and although it can change form it cannot be created or destroyed, a principle known as the conservation of energy.

Two central forms in mechanics are kinetic energy and potential energy. Kinetic energy is the energy a body possesses because of its motion and depends on its mass and the square of its speed. Gravitational potential energy is stored energy that depends on an object's mass, the strength of gravity and its height above a reference level. As an object falls, potential energy converts into kinetic energy, and in the absence of friction the total mechanical energy stays constant.

Power measures how quickly work is done or energy is transferred, defined as work divided by the time taken. A machine that completes the same task in less time delivers more power. These quantities allow engineers to compare engines, lifts and other devices on a common basis. The energy approach is often simpler than tracking individual forces, because conservation laws let the final state be predicted directly from the initial conditions.

Frequently asked questions

What is the scientific definition of work?

Work is the energy transferred when a force moves an object along the direction of that force. If there is no movement, or the force is perpendicular to the motion, no work is done.

How are kinetic and potential energy related?

They are interchangeable forms of mechanical energy. A falling object converts gravitational potential energy into kinetic energy, and the total remains constant when friction is negligible.

What does power measure?

Power measures the rate at which work is done or energy is transferred. The same amount of work performed in less time corresponds to greater power.