Work, power and efficiency

• Energy is a key principle in physics, allowing work to be done.
• The rate at which energy is transferred is called power and the amount of energy that is usefully transferred is called efficiency.
• Electrical appliances use energy and work.
• When a force causes a body to move, work is being done on the object by the force.
• Work is the measure of energy transfer when a force (F) moves an object through a distance (d).
• One joule of work is done (or one joule of energy is transferred) when a force of one newton causes a body to move through a distance of one metre.
• A horizontal force of 50 N causes a trolley to move a horizontal distance of 30 m, so the work done on the trolley by the force is 1,500 J.
• 12,000 J of energy is supplied to move a small truck a distance of 80 m, indicating the size of the force applied is 150 N.