Physics,
one step at a time.

For s = ut + ½at²: ut has (m s⁻¹)(s) = m and at² has (m s⁻²)(s²) = m, matching s. Each distractor equates quantities with different base dimensions.

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

For an isolated collision, momentum is conserved in both types. A perfectly elastic collision also conserves total kinetic energy; an inelastic collision transfers some kinetic energy to other forms.

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

Moment = force × perpendicular distance from the pivot. Increasing the lever arm increases turning effect for the same force; gears similarly transmit rotational effects.

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

Kinetic energy is ½mv², so doubling speed multiplies the squared speed and therefore kinetic energy by four. This strongly affects energy dissipated in a collision.

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

A permanent extension after unloading is plastic deformation and indicates that the spring was taken beyond its elastic behaviour. Loading and unloading data reveal this hysteresis or permanent change.

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

In a transverse wave, oscillations are perpendicular to the direction of energy transfer. In a longitudinal wave, oscillations are parallel and form compressions and rarefactions.

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

Superposition states that resultant displacement is the algebraic sum of individual displacements. Measuring individual and combined signals as path difference changes tests constructive and destructive addition.

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

A variable resistor is drawn as the resistor symbol with a diagonal arrow. Standard symbols make circuit diagrams unambiguous and should be connected with straight wires.

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

Beta decay includes an emitted (anti)neutrino, so the available energy can be divided in different proportions. In a particular two-body alpha transition, conservation laws fix the alpha particle's discrete energy.

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

Velocity is a vector, so changing direction means acceleration even at constant speed. A centripetal resultant force acts toward the centre while instantaneous velocity is tangential.

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

The shell theorem makes the external field of a spherically symmetric body equal to that of its total mass concentrated at the centre. Distance r is measured from the centre.

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

A material thermometer relies on a property such as volume or resistance. Thermodynamic temperature is defined independently of any particular working substance and has an absolute zero.

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

The model assumes point-like particles, random motion, negligible intermolecular forces except during collisions, and perfectly elastic collisions. A distribution of speeds is expected.

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

Internal energy is a state function. For the same material in the same state, the internal energy per unit mass is fixed even if the samples reached that state by different processes.

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

In ideal SHM, angular frequency is set by system parameters such as k/m or g/L in the small-angle model, not by amplitude. The oscillator is isochronous.

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

Matter contains positive and negative charges. When their totals are equal, they cancel to give zero net charge even though charged particles remain.

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

The charging model predicts V against t. A high-resistance sensor minimises loading; regular time-stamped readings allow the exponential approach to the supply to be tested safely.

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

Rotation changes magnetic flux through the coil. The direction of cutting field lines reverses every half-turn, so the induced potential difference alternates.

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

On positive and negative input half-cycles, alternate diode pairs conduct. The connections steer both currents through the load in the same direction, giving full-wave rectification.

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

Ultraviolet photons can transfer enough energy to surface electrons for emission, so negative charge leaves and the leaf collapses. The threshold behaviour supports photons.

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

The lead collimator selects directions, the scintillator converts gamma energy to light, photomultipliers convert and amplify light signals, and the computer estimates event position and builds the image.

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

An ideal black body is a perfect absorber. By thermal-radiation principles it also has maximum emissive power for its temperature, with a continuous spectrum whose shape depends on temperature.

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

Keeping lamp type and supply potential difference constant isolates circuit arrangement as the independent variable. Changing several factors together would make the cause of a brightness difference unclear.

Watch for: Do not substitute numbers before stating the relationship used for Paper 3: Advanced practical skills. Convert units first and explain what the calculated result means.

Human reaction time is a large fraction of one period. Timing N oscillations makes the measured interval about N times larger while the start/stop uncertainty is similar; T = total time/N therefore has a smaller percentage uncertainty.

Watch for: Do not substitute numbers before stating the relationship used for Paper 5: Planning, analysis and evaluation. Convert units first and explain what the calculated result means.