Distance-time graph
- A distance-time graph is a graph which shows:
- They tell us how far an object has travelled over a period of time.
Finding the distance
Section titled “Finding the distance”- If we want to find the distance travelled at a specific time, we can read it
off the graph:
- Find the time on the x-axis.
- Move vertically up to the line on the graph.
- Move horizontally to the y-axis to read off the distance.
Find the distance travelled by the object at 4 seconds
Section titled “Find the distance travelled by the object at 4 seconds”(distance, $m$)24 | / | /20 | / | /16 | / | /12 | / | / 8 | / | / 4 | / | / 0 | / |________________________________ 0 1 2 3 4 5 6 7 8 9 10 (time, $s$)Read off the graph at 4 seconds:
(distance, $m$)24 | / | /20 | / | /16 | / | /12 |-------------/ | / | 8 | / | | / | 4 | / | | / | 0 | / | |_____________|__________________ 0 1 2 3 4 5 6 7 8 9 10 (time, $s$)At 4 seconds, the distance is 12 m.
Answer:
Finding the speed / velocity
Section titled “Finding the speed / velocity”To find the speed (or velocity) of an object from a distance-time graph, we need to find the gradient at that point.
If the distance-time graph is a straight line, the speed is constant, and we can
find the gradient of the line using
If it’s not a straight line, we can draw a tangent to the curve at the point we want to find the speed, and then find the gradient of that tangent line.
Finding the average speed
Section titled “Finding the average speed”To find the average speed over a period of time, we can use the formula:
For example, to find the average speed between 2 seconds and 6 seconds:
- Assume the distance at 2 seconds is 8 m, and at 6 seconds is 20 m.
- Total distance =
- Total time =
- Average speed =