Work, kinetic energy and the work–energy theorem

Learning objectives

Calculate the work done by a constant force as W = Fd cos θ, explain when that work is positive, negative or zero, and find the work done by a varying force from the area under a force–displacement graph

Define translational kinetic energy as ½mv² and apply the work–energy theorem to relate the net work done on a system to the change in its kinetic energy

Distinguish energy transferred into or out of a system by an external force from energy transformed within the system between different forms

Define power as the rate of energy transfer and calculate average and instantaneous power using P = W/Δt and P = Fv cos θ, giving answers in watts

Construct and interpret an energy bar chart for a process, stating the system chosen and showing how the chart expresses conservation of energy