NCEA L1 Physics & ESS key terms

The rate at which an object's displacement changes, including both its speed and the direction it moves. It is a vector quantity, so a change in direction counts as a change in velocity even when speed stays constant.

The rate at which velocity changes over time. It occurs when an object speeds up, slows down, or changes direction. Measured in metres per second squared (m s⁻²) and is a vector quantity.

The straight-line distance and direction from an object's starting point to its finishing point. Unlike distance travelled, it depends only on the start and end positions, not the path taken.

A quantity that has both size (magnitude) and direction, such as force, velocity, or displacement. Vectors are shown by arrows whose length represents size and whose direction shows which way the quantity acts.

A quantity that has size (magnitude) only and no direction, such as mass, time, speed, or temperature. Scalars add like ordinary numbers, unlike vectors which must be combined using direction.

How fast an object moves, calculated as distance travelled divided by time taken. It is a scalar quantity, so it gives no information about direction of travel.

A push or pull that can change an object's speed, direction, or shape. Force is a vector measured in newtons (N), and an object's motion changes only when the forces on it are unbalanced.

The single overall force resulting from combining all forces acting on an object. If the net force is zero, the object stays at rest or keeps moving at constant velocity; a non-zero net force causes acceleration.

Two or more forces acting on an object that cancel each other out, giving a net force of zero. The object then remains stationary or continues moving at a constant speed in a straight line.

The SI unit of force, symbol N. One newton is the force needed to accelerate a one-kilogram mass at one metre per second squared, and it is used for all force measurements in physics calculations.

The amount of matter in an object, measured in kilograms. Mass measures an object's resistance to being accelerated and stays the same wherever the object is, unlike weight which changes with gravity.

The force gravity exerts on an object's mass, calculated as mass multiplied by gravitational field strength (W = mg). Measured in newtons, it changes with the strength of gravity, such as on the Moon.

The tendency of an object to resist changes in its motion. An object at rest stays at rest and a moving object keeps moving unless a net force acts on it, and objects with greater mass have more inertia.

An object stays at rest or moves at constant velocity unless a net force acts on it. This law explains why seatbelts and friction matter and why objects keep moving when no force slows them.

The acceleration of an object depends on the net force acting on it and its mass, expressed as F = ma. Doubling the force doubles acceleration, while doubling the mass halves it.

For every action force there is an equal and opposite reaction force acting on a different object. For example, when you push a wall, the wall pushes back on you with the same size force.

A force that opposes motion when two surfaces slide or try to slide past each other. It converts kinetic energy into heat and can be reduced by lubrication or by using smoother surfaces.

The energy an object has because of its motion, calculated as ½mv². It increases with mass and with the square of speed, so doubling speed gives four times the kinetic energy.

Stored energy that an object has because of its position or state, such as gravitational potential energy due to height or elastic energy in a stretched spring. It can be converted into other forms.

Energy cannot be created or destroyed, only changed from one form to another. The total energy in a closed system stays constant, though some may spread out as heat or sound.

The change of energy from one form to another, such as electrical energy becoming light and heat in a lamp. Some energy is always transferred to the surroundings, often as heat.

A graph plotting distance travelled against time. The slope of the line gives speed: a horizontal line means the object is stationary, while a steeper line means faster motion.

The electrical potential difference between two points, measured in volts (V). It is the energy transferred per unit charge, and a larger voltage pushes more current through a given resistance.

The rate at which electric charge flows past a point in a circuit, measured in amperes (A). In a series circuit the current is the same at every point, but it splits across parallel branches.

How much a component opposes the flow of electric current, measured in ohms (Ω). Higher resistance means less current for the same voltage, and resistance can change with temperature or component type.

The relationship stating that voltage equals current multiplied by resistance (V = IR) for a component at constant temperature. It lets you calculate any one of the three quantities when the other two are known.

A circuit in which components are connected one after another in a single loop. The same current flows through every component, and the total resistance is the sum of the individual resistances.

A circuit in which components are connected across the same two points, forming separate branches. The voltage across each branch is the same, and the total current is shared between branches.

A disturbance that transfers energy from one place to another without transferring matter. Waves can be mechanical, needing a medium, or electromagnetic, which can travel through a vacuum.

The distance between one point on a wave and the next identical point, such as from one crest to the next. Measured in metres and represented by the symbol λ.

The number of complete waves passing a point each second, measured in hertz (Hz). A higher frequency means more waves per second and a shorter wavelength for the same wave speed.

The maximum displacement of a wave from its resting position, measured from the middle to a crest or trough. Larger amplitude means the wave carries more energy, which for sound means a louder sound.

The bending of a wave as it passes from one medium into another at an angle, caused by a change in speed. It explains why a straw looks bent in a glass of water.

The bouncing back of a wave when it hits a surface or boundary. For a flat mirror the angle of incidence equals the angle of reflection, and this applies to light and sound alike.

One of several large slabs of solid rock that make up Earth's outer shell and slowly move over the mantle. Their movements cause earthquakes, volcanic activity, and the building of mountain ranges.

The edge where two tectonic plates meet, which can be convergent (colliding), divergent (separating), or transform (sliding past). Most earthquakes and volcanoes occur along these zones.

The process where a denser oceanic plate sinks beneath a lighter continental or oceanic plate at a convergent boundary. It creates deep ocean trenches, volcanic arcs, and powerful earthquakes.

The transfer of heat through a fluid as warmer, less dense material rises and cooler, denser material sinks. In Earth's mantle this circulation is a key driving force behind the movement of tectonic plates.

A sudden release of stored energy in Earth's crust, usually along a fault, that sends seismic waves through the ground. Its size is measured by magnitude, and its effects by intensity.

A break or fracture in rock along which movement has occurred. Stress builds up along faults until the rock slips suddenly, releasing energy as an earthquake.

A vibration that travels through Earth carrying energy released by an earthquake. P waves arrive first and travel through solids and liquids, while slower S waves travel only through solids.