1.1 Motion

Distance

how far an object moves along its path

Displacement

how far an object has travelled from its starting point

Speed

the rate of change of distance

The equation linking average speed, distance travelled and time taken

Average speed = distance travelled ÷ time taken

The equation linking average speed, initial speed and final speed

Average speed = (initial speed + final speed) ÷ 2

The equation linking acceleration, final speed, initial speed and time taken

acceleration = (final speed – initial speed) ÷ time taken

Unit for speed and velocity

Metres per second (m/s)

Unit for distance

Metres (m)

Unit for time

Seconds (s)

Unit for acceleration/ rate of change of speed

Metres per second squared (m/s²)

Typical walking speed

Approx. 1.5 metres per second (m/s)

Typical running speed

Approx. 3 metres per second (m/s)

Typical cycling speed

Approx. 6 metres per second (m/s)

Typical speed of a car

Approx. 25 metres per second (m/s)

Typical speed of a train

Approx. 50 metres per second (m/s)

Typical speed of an aeroplane

Approx. 250 metres per second (m/s)

Speed of sound in air

Approx. 330 metres per second (m/s)

Distance-time graph

A graph with distance on the y-axis and time on the x-axis

Horizontal line on a distance-time graph

Represents a stationary object

Inclined line on a distance-time graph

Represents an object moving at a constant speed

Curved line on a distance-time graph

Represents an object that is accelerating/ decelerating

How to calculate the speed of an object from a graph

Gradient of a distance-time graph

Finding speed from a non-linear distance-time graph

Draw a tangent to the curve and find the gradient of the tangent

Velocity-time graph

A graph with velocity on the y-axis and time on the x-axis

Horizontal line on a velocity-time graph

Represents an object moving at a constant speed

Inclined line on a velocity-time graph

Represents an object accelerating at a constant rate

How to calculate the acceleration of an object from graph

Gradient of a velocity-time graph

How to calculate the distance-travelled by an object from graph

Area under a velocity-time graph

Finding distance travelled from a non-linear velocity-time graph

Can be found by counting the squares beneath the line

Velocity

The speed of an object in a particular direction

The equation linking average velocity, displacement and time

Average velocity = displacement ÷ time

The equation linking average velocity, initial velocity and final velocity

Average velocity = (initial velocity + final velocity) ÷ 2

Acceleration

The rate of change of velocity over a specific time

The equation linking acceleration, final velocity, initial velocity and time

Acceleration = (final velocity – initial velocity) ÷ time

Retardation

When an object is slowing down and its acceleration has a negative value