Physics·General Physics · NSSCO 2.10.4-2.10.5
Work & power
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Four everyday words — work, energy, efficiency and power — become four precise physics ideas here, each with its own formula. We define work as W = F × d (measured in joules), meet the two mechanical energies KE = ½ m v² and GPE = m g h, watch a pendulum trade them back and forth to show the conservation of energy, measure how much energy actually does the job with efficiency, and finish with power — the rate of doing work (1 W = 1 J/s). Every formula gets a slow worked example.
What you'll learn in this lesson
By the end you should be able to (NSSCO Physics 2.10.4-2.10.5):
- Describe energy transfer in terms of work done, and recall and use W = F × d (with the joule as the unit of work and energy, 1 J = 1 N m)
- Recall and use the formula for kinetic energy, KE = ½ m v²
- Recall and use the formula for gravitational potential energy, GPE = m g h
- State and apply the principle of conservation of energy (e.g. kinetic ↔ gravitational potential energy in a pendulum)
- Define efficiency and recall and use efficiency = useful energy output ÷ total energy input × 100%
- Define power as the rate of doing work and recall and use P = W ÷ t = E ÷ t (1 W = 1 J/s)
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Ms Elizabeth and Mike talk through the whole topic — with the figure and working drawn live.