QCAA Physics flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Constant acceleration equation

v = u + at relates final and initial velocity to acceleration and time, and applies only when acceleration is uniform over the interval considered.

Velocity–time graph gradient

The gradient of a velocity–time graph equals acceleration, while the area between the line and the time axis equals displacement during that interval.

Newton's second law

The net force on an object equals its mass times acceleration, ΣF = ma; the net force and acceleration are always in the same direction.

Kinetic energy

Kinetic energy is ½mv², the energy an object possesses due to motion; doubling speed quadruples kinetic energy because of the squared velocity term.

Conservation of momentum

In an isolated system with no net external force, total momentum before an interaction equals total momentum after, expressed as Σmv constant.

Centripetal acceleration

For uniform circular motion, acceleration points toward the centre with magnitude v²/r, arising from the net inward force acting on the object.

Snell's law

n₁sinθ₁ = n₂sinθ₂ describes refraction at a boundary, where n is refractive index and angles are measured from the normal.

Total internal reflection condition

Total internal reflection requires light travelling from a higher to a lower refractive index and an incidence angle greater than the critical angle.

Projectile motion components

Horizontal and vertical motions are independent: horizontal velocity stays constant while vertical acceleration is g downward, giving a parabolic path.

Orbital speed relation

Setting gravitational force equal to centripetal force gives v = √(GM/r), so orbital speed decreases as orbital radius increases.

Electric field strength

Electric field strength E = F/q is force per unit positive charge; for a point charge its magnitude is kQ/r², directed radially.

Faraday's law

The induced emf in a coil equals the negative rate of change of magnetic flux linkage, ε = −NΔΦ/Δt, with flux Φ = BA cosθ.

Lorentz factor

γ = 1/√(1 − v²/c²) quantifies relativistic effects; it approaches one at low speeds and grows without bound as speed nears c.

Adding uncertainties

When quantities are added or subtracted, their absolute uncertainties add; when multiplied or divided, their percentage uncertainties add.

Percentage uncertainty

Percentage uncertainty equals the absolute uncertainty divided by the measured value, multiplied by one hundred, expressed as a percentage.

Linearising a graph

Data are transformed so the plotted relationship is a straight line; the gradient and intercept then correspond to specific physical constants or parameters.

Analogue reading uncertainty

For a single analogue measurement, absolute uncertainty is commonly taken as half the smallest scale division of the instrument used.

Significant figures rule

A calculated result should be reported with the same number of significant figures as the least precise measurement used in the calculation.

Percentage difference

Percentage difference compares an experimental value with an accepted value, calculated as the absolute difference divided by the accepted value times one hundred.

Testable research question

A research question suitable for investigation identifies the independent variable, dependent variable, and the conditions held constant during the experiment.

Validity in experiments

Validity means the experiment measures what it claims to measure, requiring control of all variables except the independent variable.

Reliability in experiments

Reliability is the consistency of repeated measurements, improved by multiple trials, consistent technique, and careful instrument calibration.

Accuracy in measurement

Accuracy is closeness to the true value, improved by finer instrument resolution, zero-error correction, and removal of systematic error.

Random versus systematic error

Random error scatters measurements unpredictably around a value and is reduced by averaging; systematic error shifts all readings consistently in one direction.

Control group purpose

A control group is a baseline without the independent variable, allowing any observed effect to be attributed to that variable rather than other factors.

Secondary evidence evaluation

Secondary evidence is judged by authority, peer review, recency, methodological transparency, and independence from commercial or ideological interests.

Evaluating a scientific claim

A claim is judged supported, partially supported, or refuted based on the consistency, strength, and relevance of the synthesised evidence.

Synthesis of sources

Synthesis combines findings from multiple credible sources, explicitly identifying where they agree, where they conflict, and why.

Limitations in research

Limitations are constraints on the conclusions, such as small samples, conflicting literature, narrow conditions studied, or extrapolation beyond the evidence.

Credible source criteria

Credible sources are peer reviewed, authored by qualified experts, recently published, transparent about method, and free from commercial bias.

Referencing purpose

Complete, consistent referencing allows every factual claim to be traced to its source and acknowledges the work of other researchers.

Extrapolation risk

Extrapolation applies findings beyond the conditions actually studied, which weakens conclusions because the underlying relationship may change.