* Work is done when a force causes displacement in the direction of the force.

* When you apply force at an angle, only the component of the force that's parallel to the direction of movement does work. The component perpendicular to the motion doesn't contribute to work.

Example:

Imagine pushing a box horizontally across the floor. If you push straight ahead (force parallel to motion), you do the most work. If you push at an angle (part of the force is upward), you do less work because you're also lifting the box slightly.

Key point: The formula for work is W = Fd cos(θ), where θ is the angle between the force and the displacement. This equation shows how only the component of force parallel to displacement (F cos(θ)) contributes to work.