Distance-time graphs
For a moving object, the distance travelled can be represented by a distance-time graph.
A horizontal line on a distance-time graph shows that the object is stationary (not moving), while a sloping line on a distance-time graph shows that the object is moving.
The The distance travelled in a known time period, eg miles per hour or kilometres per hour. of an object can be calculated from the Another word for steepness. On a graph, the gradient is defined as being the change in the 'y' value divided by the change in the 'x' value. It defines how steep a line is. of a distance-time graph.
Example
Calculate the speed of the object represented by the green line in the graph, from 0 to 4 s.
change in distance = (8 – 0) = 8 m
change in time = (4 – 0) = 4 s
\( speed = \frac{distance}{time} \)
\( speed = 8 \div 4 \)
\( speed = 2 \ m/s \)
Question
Calculate the speed of the object represented by the purple line in the graph.
change in distance = (10 - 0) = 10 m
change in time = (2 - 0) = 2 s
\( speed = \frac{distance}{time} \)
\( speed = 10 \div 2 \)
\( speed = 5 \ m/s \)