Achieve Your Highest Grade
Home  Premium Plan  Students  Parents  Teachers  Past Papers  A Level Physics  Shop
Reading Graphs
Linear Graphs and y = mx + c
A graph that has a straight line is called a linear graph:

The vertical axis is the yaxis, while the horizontal axis is called the xaxis

The gradient, or slope, of the line is given the symbol 'm'

The line crosses the yaxis when x = 0 at the yintercept, given the symbol 'c'
Calculating the gradient, or slope, of a linear graph is an important skill to master:

Draw a large triangle onto the line

Work out the coordinates of the two points where the triangle meets the line

Divide the change in y value by the change in x value
Calculating Gradients: Example A
A worked example where the gradient of a straight line is calculated.
Drawing Tangents to a Curve [often higher tier only]
Sometimes you need to work out the slope at a particular point on a curve:

Carefully draw a straight line with a ruler that just touches the curve

Work out the gradient of this straight line in the usual way
Tangents: Example
A worked example where a tangent is used to find the gradient of a curve at a point.
Calculating the Area under a Graph
This is how to calculate the area under a line on a graph. It's simple maths: you just need to break up the shape into triangles and squares, take care with your readings and then work methodically through it.
This is a really important skill to master, especially as you may need to use it when calculating the displacement from a velocitytime graph.
You may also be interested in...