Chapter 5: Work, Energy and Power

Work, Energy and Power is the chapter that hands you physics' most powerful shortcut: the energy ledger. Chapters 2–3 described how things move, and Chapter 4 explained why — forces. But tracking forces through a curved, speeding, spring-loaded problem is slow arithmetic; energy asks only for the endpoints. This hub maps the complete chapter: the work-energy theorem (W_net = ΔK) built on kinetic energy K = ½mv² and the v² − u² = 2as identity you already own; work by a constant force with its sign discipline and zero-work trio; variable-force work read as the area under the F–x graph; potential energy and the conservative-force test; conservation of mechanical energy with friction bookkeeping; the spring and its ½kx² reservoir; power in watts, horsepower and kilowatt-hours; and the full collision taxonomy — where momentum from the momentum-conservation page meets kinetic energy for the first time. The exam pattern is famously mechanical: F–x area numericals, energy-conservation chains with springs, P = Fv engine problems, unit-conversion MCQs (kWh is energy, not power), and elastic-collision special cases. Work through the eight topic pages below in order, drill each page's practice questions, then sit the 30-question chapter test with its full answer key.