Information about answering questions about graphs in IGCSE Edexcel Physics. For more notes and helps, visit http://www.shawonnotes.com

1. IGCSE Edexcel Physics
Graphs
Practical Questions

2. IGCSE Edexcel Physics
Getting Started
Students are required to know:
• To calculate gradient of the graph
• To sketch “line of best fit” and “curve of
best fit”
• Types of graphs: line and bar chart and
when and where to use them.
• Shapes of graph

3. IGCSE Edexcel Physics
Calculating gradient
• Gradient of straight line can be
calculated by the following equation
𝑚 =
(𝑦2−𝑦1)
(𝑥2−𝑥1)
• Example: From the right hand graph
𝑚 =
(𝑦2−𝑦1)
(𝑥2−𝑥1)
𝑚 =
8 − 6
10 − 6
= 𝟎. 𝟓

4. IGCSE Edexcel Physics
Independent variable vs Dependent
variable
• The independent
variable is always on
the horizontal x-axis,
and the dependent
variable is always on
the vertical y-axis as
shown on the right.

5. IGCSE Edexcel Physics
Types of graph
There are many kinds of graph. Graphs with
axis (x and y) are basically two types:
• Line graph
• Bar chart
• Lines charts are used for continuous
variables and Bar chart are used of
discontinuous variables.

6. IGCSE Edexcel Physics
Line of best fit
• Line of best fit is
the line that is the
most closest to all
the points.
• It also helps
discard
anomalous
readings

7. IGCSE Edexcel Physics
Curve of best fit
• The curve of best
fit needs to be
smooth and close
to most of its
readings
• It doesn’t
necessarily have to
join all the points in
the graph

8. IGCSE Edexcel Physics
Describing Shapes of Graph
• Linear relationship: If a graph produce a straight line,
then the relationship between the two variables is linear.
• Non-linear relationship: If the graph is curved, then the
relationship is non-linear.

9. IGCSE Edexcel Physics
Describing Shapes of Graph
• Graphs often pass through origin
• Positive/negative correlation: If the gradient of the graph
is positive, then it has positive correlation. If the gradient
is negative, then the graph has negative correlation
• Inverse relationship: The relationship is said to be
inverse if the correlation is negative. That is, if one
variable’s value increase, the other’s decrease.

10. IGCSE Edexcel Physics
Tips
Graphs are often marked for the following
features:
• Size: your graph should cover more than
50% of the graph paper
• Axis: Label quantity and unit, keep
numbers evenly spaced