Scalar and Vector Quantities, Motion, and Forces

Scalar Quantities

Scalars are quantities that have only magnitude (size), with no direction.

Speed

how fast something is moving, regardless of direction.

Distance

how far something has travelled, not where.

Mass

amount of matter in an object.

Time

the duration of an event.

Energy

total amount of work done or heat transferred.

Temperature

measure of thermal energy.

Key idea of Scalars

Scalars are described with a number and unit only (e.g. 5 m, 20 kg, 60 s).

Vector Quantities

Vectors are quantities that have both magnitude and direction.

Velocity

speed in a specific direction (e.g. 30 m/s north).

Displacement

distance in a particular direction.

Force

push or pull in a direction.

Acceleration

rate of change of velocity in a direction.

Momentum

mass × velocity, includes direction.

Key idea of Vectors

Vectors must include direction to be fully described.

Speed vs Velocity

Speed is scalar (e.g. 60 km/h), velocity is vector (e.g. 60 km/h east).

Distance vs Displacement

Distance is scalar (total path), displacement is vector (straight-line from start to finish with direction).

How to Identify a Vector

Ask: Does direction matter for this quantity? If yes → it's a *vector. If no → it's a scalar*.

Representing Vectors

Vectors are often shown as *arrows*: Length of the arrow = magnitude. Direction of the arrow = direction of the quantity.

In Exams

You may be asked to: Identify scalar or vector quantities from a list. Compare speed and velocity. Use vector diagrams to show forces or motion.