Calculate changes in energy when a system is changed by work done by forces.

Force-based work questions begin with W = Fs. In the Energy stores and systems subtopic, a force acting through a distance transfers energy mechanically, such as lifting a mass, stretching a spring, or moving an object along a surface. This differs from heating because temperature change is not the key evidence, and differs from electrical transfer because current is not the cause. A strong response states the force in newtons, distance in metres, work in joules, and the energy stores involved.