Graphical representation of motionCopy

Learning Objectives

• Calculate speed from the gradient of a distance–time graph
• Plot and interpret a speed–time graph or a distance–time graph
• Recognise from the shape of a speed–time graph when a body is
  –– at rest
  –– moving with constant speed
  –– moving with changing speed
• Calculate the area under a speed–time graph to work out the distance travelled for motion with constant acceleration.
• Recognise linear motion for which the acceleration is constant
• Recognise motion for which the acceleration is not constant
• Calculate acceleration from the gradient of a speed–time graph
• Understand deceleration as a negative acceleration
• Demonstrate understanding that acceleration and deceleration are related to changing speed including qualitative analysis of the gradient of a speed–time graph

Contents to learn

Graphs

It is a pictorial form of data.

In IGCSE Physics, we always plot the graph between two sets of values (2D graph).

Independent set of value is always taken along x-axis.

Dependent set of value is always taken along y- axis.

If graph is straight line and passes through the origin then the quantities along both the axes are proportional to each other

Distance – time graph

Time always runs horizontally (along x-axis).

Distance always runs vertically (along y-axis).

The slope of distance time graph gives us speed.

Speed is a scalar quantity.

The unit of speed is m / s.

Speed – time graph

The area under the speed time – graph gives us distance.
Distance is a scalar quantity.
The unit if distance is meters (m).