Real Life Graphs

What the picture shows

• A travel graph puts distance on the vertical axis and time on the horizontal one, so the line traces a journey
• The vertical axis usually reads "distance from" a named place, so it shows position rather than distance covered
• A sloping line means movement, and the steeper it is the faster the journey
• A line sloping up leads away from the starting place; one sloping down comes back towards it
• A horizontal line means the distance is not changing, so the traveller has stopped
• Times along the bottom are usually written in 24-hour clock form

Speed from the graph

• The gradient of a sloping section is the speed of that section
• Speed is the distance covered divided by the time taken, so read both from the grid and divide
• Take the units from the axes: kilometres against hours gives km/h, metres against seconds gives m/s
• Convert a time read in minutes to hours before dividing, or the speed comes out sixty times too small
• The average speed for a whole journey is the total distance divided by the total time, and the total time includes every stop