Physics,
one step at a time.

Energy is measured in joules and power in watts. Force uses newtons, mass kilograms, charge coulombs, current amperes, pressure pascals and distance metres.

Watch for: Do not substitute numbers before stating the relationship used for Key concepts of physics. Convert units first and explain what the calculated result means.

Reaction time varies naturally, but an outlier may reflect anticipation, distraction or measurement error. Repeats improve reliability; a justified treatment of anomalies produces a more representative mean.

Watch for: Do not substitute numbers before stating the relationship used for Motion and forces. Convert units first and explain what the calculated result means.

Nuclear stations can deliver continuous high output with low operational carbon emissions, but waste management, accident risk and lifecycle costs require evaluation.

Watch for: Do not substitute numbers before stating the relationship used for Conservation of energy. Convert units first and explain what the calculated result means.

A microphone converts the sound to an electrical signal displayed against time. Measuring several cycles reduces percentage uncertainty; frequency is the reciprocal of period.

Watch for: Do not substitute numbers before stating the relationship used for Waves. Convert units first and explain what the calculated result means.

Alternating currents accelerate charges in an aerial, producing radio waves. Their electric fields drive oscillating currents in a receiving aerial. Atomic and nuclear changes can produce higher-frequency electromagnetic radiation.

Watch for: Do not substitute numbers before stating the relationship used for Light and the electromagnetic spectrum. Convert units first and explain what the calculated result means.

Positive nuclei repel. Extremely high temperature supplies kinetic energy for close approach, while adequate density and confinement are needed long enough for useful fusion without losing more energy than is produced.

Watch for: Do not substitute numbers before stating the relationship used for Radioactivity. Convert units first and explain what the calculated result means.

Objects and processes emit characteristic wavelengths. Space telescopes avoid atmospheric absorption for some bands, while larger and linked detectors improve sensitivity and angular resolution.

Watch for: Do not substitute numbers before stating the relationship used for Astronomy. Convert units first and explain what the calculated result means.

Energy is transferred from the spring's elastic store to the trolley's kinetic store, with some dissipated thermally. Energy is conserved in the complete system.

Watch for: Do not substitute numbers before stating the relationship used for Energy: forces doing work. Convert units first and explain what the calculated result means.

A free-body diagram isolates one object and shows each external force with direction and, where useful, relative magnitude. It supports vector addition and equilibrium reasoning.

Watch for: Do not substitute numbers before stating the relationship used for Forces and their effects. Convert units first and explain what the calculated result means.

Adding a parallel branch increases total conductance. Both branches have the same potential difference and junction currents add, so total current is greater and R = V/I is below either branch resistance.

Watch for: Do not substitute numbers before stating the relationship used for Electricity and circuits. Convert units first and explain what the calculated result means.

The rod's field redistributes charge in the paper. The nearer induced positive region experiences a stronger attraction than the repulsion of farther negative charge, giving a net attraction.

Watch for: Do not substitute numbers before stating the relationship used for Static electricity. Convert units first and explain what the calculated result means.

Soft magnetic materials respond strongly while current flows but lose most magnetism when current stops, which suits switchable electromagnets.

Watch for: Do not substitute numbers before stating the relationship used for Magnetism and the motor effect. Convert units first and explain what the calculated result means.

An alternating primary current produces changing flux in the iron core. This changing flux links the secondary coil and induces an alternating potential difference.

Watch for: Do not substitute numbers before stating the relationship used for Electromagnetic induction. Convert units first and explain what the calculated result means.

The piston does mechanical work on the gas. Before substantial heat escapes, internal energy and temperature rise; reduced volume also increases collision rate and pressure.

Watch for: Do not substitute numbers before stating the relationship used for Particle model. Convert units first and explain what the calculated result means.

Atmospheric pressure arises from the weight and molecular impacts of the air above. At greater altitude there is less overlying air and usually lower density, so pressure falls.

Watch for: Do not substitute numbers before stating the relationship used for Forces and matter. Convert units first and explain what the calculated result means.