WACE ATAR Physics key terms

The straight-line distance and direction from an object's starting point to its current position, forming a vector quantity that differs from the total path length travelled.

The rate at which an object's displacement changes over time, including its direction; the gradient of a displacement-time graph gives this quantity.

The rate at which velocity changes with time, whether speeding up, slowing down, or changing direction; measured in metres per second squared and caused by a net force.

The total length of the path actually travelled by an object, regardless of direction, making it a scalar quantity measured in metres.

How fast an object covers distance, calculated as distance divided by time; a scalar quantity with no direction attached.

The single vector sum of all individual forces acting on an object, which determines the object's acceleration according to Newton's second law.

A simplified drawing showing an object as a point and representing every external force acting on it as an arrow with correct direction and relative size.

The support force a surface exerts perpendicular to itself on an object resting or sliding against it, balancing part or all of the object's weight.

A contact force that opposes relative motion or the tendency to move between two surfaces, converting kinetic energy into thermal energy and internal energy.

An object remains at rest or moves with constant velocity unless acted on by a net external force; often called the law of inertia.

The tendency of an object to resist changes to its state of motion, determined entirely by its mass and independent of the forces acting on it.

A measure of the amount of matter in an object and of its resistance to acceleration, remaining constant regardless of location in the universe.

The gravitational force an object experiences due to a nearby massive body, calculated as mass multiplied by gravitational field strength and measured in newtons.

The product of an object's mass and velocity, a vector quantity describing how difficult it is to stop the object; conserved in isolated systems.

The change in momentum caused by a force acting over a time interval; equal to force multiplied by time and measured in newton seconds.

In a closed system with no external net force, the total momentum before an interaction equals the total momentum after it, applying to collisions and explosions.

A collision in which both total momentum and total kinetic energy are conserved, with no energy permanently transformed into deformation, heat, or sound.

A collision in which momentum is conserved but total kinetic energy is not, because some energy is converted into deformation, heat, or sound.

The energy transferred to or from an object when a force acts on it through a displacement; calculated as the component of force along the displacement times distance.

The energy an object possesses because of its motion, calculated as half its mass multiplied by the square of its speed.

Energy stored in a system because of the relative positions of its parts, such as an object raised against gravity or a stretched spring.

The principle that energy cannot be created or destroyed but only transformed between forms or transferred between objects, so total energy in a closed system stays constant.

The rate at which energy is transferred or work is done, calculated as energy divided by time and measured in watts.

The ratio of useful energy or power output to total energy or power input for a device, usually expressed as a percentage and always less than 100 percent for real devices.

Motion along a circular path at constant speed but changing velocity, requiring a centripetal force directed towards the centre of the circle.

The net force directed towards the centre of a circular path that keeps an object moving in that circle, proportional to mass, speed squared, and inverse radius.

The turning effect of a force about a pivot, calculated as force multiplied by the perpendicular distance from the pivot to the line of action.

The state of an object when the net force and net torque acting on it are both zero, so it remains at rest or moves with constant velocity.

A disturbance that transfers energy from one place to another without the bulk transfer of matter, characterised by wavelength, frequency, and amplitude.

The number of complete wave cycles passing a fixed point each second, measured in hertz; it equals the reciprocal of the period.

The distance between two consecutive corresponding points on a wave, such as from one crest to the next, measured in metres.

The time taken for one complete wave cycle or oscillation to occur, measured in seconds and equal to the reciprocal of frequency.

The bending of a wave as it passes from one medium into another where its speed changes, caused by a change in wavelength while frequency stays constant.

A dimensionless ratio comparing the speed of light in a vacuum to its speed in a given medium, describing how strongly that medium bends light.

The complete reflection of light back into a denser medium when it strikes a boundary beyond the critical angle, occurring because refraction is impossible.

The spreading of waves around obstacles and through gaps, becoming most pronounced when the gap width is comparable to the wavelength.

The principle that when two or more waves meet at a point, the resultant displacement equals the vector sum of the individual displacements.

The reinforcement or cancellation that occurs when waves from two sources overlap, producing patterns of constructive and destructive superposition.

A region around a charged object where another charge experiences an electric force; represented by field lines pointing from positive to negative charge.

The electric force per unit positive charge experienced at a point in an electric field, a vector quantity measured in newtons per coulomb.

The electric force between two point charges is proportional to the product of the charges and inversely proportional to the square of their separation.

A measure of the number of magnetic field lines passing through a given area, calculated as field strength times area times the cosine of the angle between them.

The generation of an electromotive force in a conductor when it experiences a changing magnetic flux, forming the basis of generators and transformers.

The induced electromotive force in a circuit equals the negative rate of change of magnetic flux through it, with the negative sign indicating the direction of opposition.

An induced current always flows in a direction whose magnetic field opposes the change in flux that produced it, a consequence of energy conservation.

The gravitational force per unit mass experienced at a point in a gravitational field, equal to the local acceleration due to gravity and measured in newtons per kilogram.

A testable, evidence-based prediction that proposes a relationship between variables, which can be supported or refuted by collecting and analysing data.

The factor deliberately changed or selected by the experimenter in an investigation to observe whether it produces a measurable effect on another variable.

The factor measured or observed in an investigation, expected to respond to changes in the independent variable and recorded as the outcome data.

A factor that is deliberately kept constant throughout an investigation so that it cannot influence the dependent variable and distort the results.

The extent to which an investigation actually measures what it claims to measure, achieved by controlling variables and using appropriate equipment and procedures.

The consistency of repeated measurements or results; improved by taking multiple readings, using precise instruments, and reducing random error.

The range within which the true value of a measurement is likely to lie, arising from limitations of instruments and random or systematic errors.

How close a measured value is to the accepted or true value, affected mainly by systematic errors rather than by random variation between readings.

A simplified representation or explanation of a real system used to make predictions and interpret observations, always limited by the assumptions it makes.

The process in which independent experts evaluate a scientist's methods, evidence, and conclusions before publication, helping to maintain quality and credibility.

A fundamental change in the dominant framework of assumptions and methods within a science, often following accumulating evidence that the old framework cannot explain.