QCAA Physics cheat sheet

Paper 1 is a multiple-choice/short-response paper sat under supervised conditions; it samples the whole syllabus, so every unit's key formulas must be recallable without a data sheet prompt.

Use v = u + at, s = ut + ½at², v² = u² + 2as only when acceleration is constant; a velocity–time gradient gives acceleration and area gives displacement.

Newton's second law is ΣF = ma; weight is W = mg with g ≈ 9.8 m/s²; friction force f ≤ μN and equals μN only at the point of slipping.

Work–energy: W = Fs cosθ, kinetic energy ½mv², gravitational potential energy mgh; total mechanical energy is conserved only when non-conservative work is zero.

Momentum p = mv is conserved in isolated systems; impulse J = FΔt = Δp; collisions are elastic only if kinetic energy is also conserved.

Circular motion: a = v²/r = 4π²r/T², centripetal force is a net force, never an extra force added to a free-body diagram.

Waves: v = fλ, T = 1/f; for a string or pipe, harmonics follow integer or odd-integer multiples of the fundamental depending on boundary conditions.

Snell's law n₁sinθ₁ = n₂sinθ₂ with n = c/v; total internal reflection occurs only when light travels from higher to lower refractive index and θ exceeds the critical angle.

Paper 2 is the extended-response/short-answer paper: it rewards full working, labelled free-body diagrams, and explicit statement of the physical principle used.

For projectile motion resolve independently: horizontal a = 0 with v_x constant; vertical a = −g, giving time of flight from vertical motion only.

For inclined planes resolve weight into mg sinθ along the slope and mg cosθ perpendicular; normal force N = mg cosθ for a frictionless incline.

Kepler and orbital relations: gravitational force provides centripetal force, so GMm/r² = mv²/r, giving v = √(GM/r) and T² ∝ r³.

Electric fields: E = F/q, E = kQ/r², V = kQ/r; field lines point from positive to negative and are perpendicular to equipotentials.

Magnetic force on a current-carrying wire F = BIL sinθ and on a moving charge F = qvB sinθ; direction from the right-hand rule.

Electromagnetic induction: ε = −NΔΦ/Δt and Φ = BA cosθ; Lenz's law sets the induced current direction to oppose the change in flux.

Special relativity: γ = 1/√(1 − v²/c²); time dilation Δt = γΔt₀ and length contraction L = L₀/γ apply to measurements between inertial frames.

The data test supplies unfamiliar data or a scenario and is completed under supervised conditions; answers must be derived from the supplied data, not recalled values.

Uncertainty rules: for addition/subtraction add absolute uncertainties; for multiplication/division add percentage uncertainties.

Percentage uncertainty = (absolute uncertainty ÷ measured value) × 100; the result carries the same percentage uncertainty as the most uncertain input.

Absolute uncertainty of a single analogue reading is typically half the smallest scale division; for a digital display it is ±1 in the last digit.

Linearise data before graphing: plot the transformed variables so the relationship is y = mx + c, then identify the gradient and intercept with their physical meanings.

Gradient uncertainty from a line of best fit is estimated from the steepest and shallowest acceptable lines through the data.

Significant figures in a final answer should match the precision of the least precise input; state units and direction where the quantity is a vector.

When comparing a calculated result with a theoretical value, quote a percentage difference and judge whether the discrepancy lies within the stated uncertainty.

The student experiment is an extended experimental investigation: a research question derived from the syllabus, a modified or extended practical, and a scientific report.

A testable research question names the independent variable, the dependent variable, and the conditions held constant.

The experiment must include a control or a baseline comparison and repeat trials (typically three or more) to allow a mean and a measure of spread.

Validity depends on controlling all variables except the independent variable and on measuring the dependent variable in a way that truly reflects the concept.

Reliability is improved by repeated trials, consistent technique, and calibration of instruments; it is reported through the spread of repeated measurements.

Accuracy is improved by choosing instruments with finer resolution, correcting for zero error, and reducing systematic error.

The report structure is: research question, rationale, methodology, results with processed data and uncertainty, analysis, evaluation of sources of error, and suggested improvements.

Evaluation must distinguish random from systematic error and propose specific, realistic improvements rather than generic statements.

The research investigation answers a research question by evaluating secondary evidence against a scientific claim, not by collecting new primary data.

A strong research question is specific, answerable from credible sources, and identifies the physical relationship being investigated.

Source quality is judged on authority, recency, peer review, methodology transparency, and independence from commercial interest.

Evidence must be synthesised across at least several credible sources, with agreement and contradiction between sources explicitly discussed.

The claim is evaluated as supported, partially supported, or refuted, with reasoning tied to the strength and consistency of the evidence.

Quantitative evidence should be compared where possible, including the conditions under which each study was conducted and whether they are comparable.

Limitations include gaps in the available literature, conflicting data, small sample sizes, and the extrapolation of results beyond the conditions studied.

Referencing must be consistent and complete so that every factual claim can be traced to a specific source.