This mini-lesson covers Theme A.3 — Work, energy and power: work done by a force, kinetic and potential energy, the conservation of energy, and power and efficiency.
Work through each screen, answer the questions as you go (some are reasoning, some are calculations) and collect ⭐ stars. Watch for the HL flag on higher-level extensions. Press Start when you're ready.
Work is energy transferred when a force moves its point of application. Only the force component along the displacement does work.
If the force is perpendicular to the motion (θ = 90°, cos90° = 0) it does no work — e.g. the tension in a string on a mass in circular motion, or the normal force on a sliding box.
Two workhorse energy formulas:
Elastic (spring) potential energy stores work done stretching a spring that obeys Hooke's law (F = kx):
A 2.0 kg mass falls Δh = 1.5 m. GPE released:
ΔEₚ = mgΔh = 2.0 × 9.81 × 1.5 = 29.4 J (this becomes kinetic energy)
Tap an item, then tap the group it belongs to.
Power is the rate of energy transfer (or rate of doing work), in watts (1 W = 1 J s⁻¹). For a force pushing something at speed v: P = Fv.
The wasted energy has not vanished — total energy is conserved. It is usually transferred to the surroundings as heat (thermal energy) and is no longer useful.
Tap a statement on the left, then its match on the right.
Work: W = Fs cosθ; zero when force ⟂ motion
Energy: Eₖ = ½mv² · ΔEₚ = mgΔh · elastic Eₚ = ½kΔx²
Conservation: energy is never lost, only transferred (often wasted as heat)
Power: P = W ÷ t = Fv, in watts
Efficiency: useful output ÷ total input, always < 1 for real machines
That completes Work, Energy & Power for IB Diploma Physics HL. Press Finish to see your score.
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