Work by Constant Force

Work done by a constant force F over displacement d is W = F·d·cos θ, where θ is the angle between F and d.

Units: joule (J) = N·m. 1 J = work done by 1 N over 1 m parallel.

Scalar quantity. Can be positive (force along motion), negative (force opposite motion), or zero (force ⊥ motion).

Force perpendicular to displacement does NO work — even though force is exerted.

Gravity does NEGATIVE work when lifting up (F downward, motion upward).

Friction (kinetic) generally does negative work on the moving object — opposes motion.

Vector form: W = F · d (dot product). For non-constant F: integrate.

Work is a TRANSFER of energy — equal to change in KE when only F acts.