Motion, Forces and Energy - Vocabulary Flashcards

Vocabulary flashcards covering key terms from motion, vectors, units, and related concepts in the notes.

SI units (Système International d’Unités)

A globally used system of units for measuring physical quantities.

Metre (m)

The base unit of length in the SI system.

Decimetre (dm)

One tenth of a metre (0.1 m).

Centimetre (cm)

One hundredth of a metre (0.01 m).

Millimetre (mm)

One thousandth of a metre (0.001 m).

Micrometre (μm)

One millionth of a metre (1×10^-6 m).

Nanometre (nm)

One billionth of a metre (1×10^-9 m).

Kilometre (km)

A thousand metres (10^3 m).

Gigametre (Gm)

One billion metres (10^9 m).

Area

The amount of surface inside a 2D shape; unit is square metre (m²); area = length × breadth.

Volume

The amount of space occupied by a 3D object; unit is cubic metre (m³), commonly cm³.

Time

A measure of duration; base unit is the second (s).

Scalar quantity

A quantity described by magnitude only (size). Example: distance, speed, mass.

Vector quantity

A quantity described by magnitude and direction. Example: force, velocity, acceleration.

Magnitude

The size or amount of a quantity, without direction.

Direction

The orientation of a vector along which it acts.

Representing vectors

A straight line with an arrow; length indicates magnitude and arrow indicates direction.

Distance

Total length of path travelled; a scalar quantity.

Displacement

Overall change in position from start to finish; a vector with direction.

Speed

Distance travelled per unit time; scalar. Formula: speed = distance/time.

Velocity

Displacement per unit time in a given direction; a vector.

Acceleration

Change of velocity per unit time; a vector.

Positive acceleration

Velocity increases; speed up in the same direction.

Negative acceleration (deceleration)

Velocity decreases; slow down or reverse direction.

Speed-time graph

Graph of speed versus time; gradient represents acceleration; area under the graph gives distance.

Gradient (on a speed-time graph)

The slope of the graph; equals acceleration.

Constant speed

A horizontal line on a speed-time graph indicating speed does not change.

Constant acceleration

A straight-line graph with nonzero slope on a speed-time graph, indicating speed changing at a steady rate.

Distance-time graph

Graph of distance versus time; gradient indicates speed.

Average speed

Total distance divided by total time (s/t).

Terminal velocity

Constant speed reached when air resistance balances weight during fall.

Air resistance (drag)

Opposing force from air acting on a moving body; more significant for light or large-surface objects.

Free fall

Motion under gravity with negligible air resistance; acceleration is g ≈ 9.8 m/s².

Gravitational field strength (g)

Acceleration due to gravity near Earth's surface, about 9.8 m/s².

SUVAT equations (motion under constant acceleration)

Set of equations: a = (v − u)/t; v = u + a t; s = ut + 1/2 a t^2; s = ((u+v)/2) t; v^2 = u^2 + 2 a s.

Velocity (revisited)

Rate of change of displacement; in a given direction; units same as speed (e.g., m/s).