Worka

Meet Worka, a character pushing a crate across the floor.

In everyday speech anything tiring is work, but in physics work has a precise meaning: energy transferred when a force moves something along the direction of the force. If the force is at an angle θ to the motion, only the part along the motion counts, so W = Fd cos θ. Work is measured in joules; one joule is one newton acting through one metre.

Pushing with 50 N for 3 m in the direction of motion does 50 × 3 × cos 0° = 150 J. Push at 60° to the motion and cos 60° = 0.5, so only 75 J. Push at right angles, θ = 90°, and cos θ = 0, so no work is done at all.

Engineers use work to size motors and lifts, and the work–energy theorem links the net work on an object to its change in kinetic energy.

Holding a heavy bag still feels like effort but does no work on the bag, because it does not move; your muscles use energy internally. The formula also assumes a constant force; a varying force needs to be added up along the path.