1.7.2 Work
- Syllabus
- 0625–2026–2027
- Topic
- 1.7.2
- Level
- —
Learning objectives
Relate work done to energy transferred
Mechanical or electrical work done is equal to the energy transferred between stores.
| Work pathway | How energy is transferred | Example |
|---|---|---|
| mechanical work | a force acts while its point of application moves | lifting transfers energy to an object's gravitational potential store |
| electrical work | moving charges transfer energy | a current transfers energy from a battery's chemical store to a motor |
Work done on an object transfers energy to it; work done by an object transfers energy away from one of its stores. Work and energy are both measured in joules (J).
A force can act without doing mechanical work if there is no displacement in the force's direction. A heavy load hanging motionless has a force on it but no mechanical work is being done on the load.
In physics, work is an energy transfer, not simply effort or tiredness. Identify the force or electrical current and the energy stores that change.
Calculate mechanical work
For a constant force acting in the direction of motion, mechanical work equals force multiplied by the distance moved in the force's direction; this equals the energy transferred.
W=Fd=ΔE
| Symbol | Meaning | SI unit |
|---|---|---|
| W | work done | J |
| F | force component in the direction of motion | N |
| d | distance moved in that direction | m |
| ΔE | energy transferred or store change | J |
Select the force doing the work, use the displacement in that force's direction, convert to SI units, multiply, and name the associated energy transfer. Rearrangements are F=W/d and d=W/F.
When several forces act, calculate their work separately or use the resultant force for the net change in kinetic energy. Work against friction transfers energy to internal stores; lifting at constant speed transfers energy to the gravitational potential store.
Do not automatically use vertical height or total path length. Use the distance moved in the direction of the selected force: along a slope for a parallel pull, but vertical height for weight.