### The gradient of a distance-time graph is the speed of an object. In a graph, distance is represented by the y axis, and time by the x axis.The steeper this line, the faster the object is moving. A stationary object is represented by a horizontal line, because time never stops.

To calculate the average speed you need to know how to read distance time graphs and how to calculate the gradient (speed!).

### Speed

The speed is just the gradient, so we divide the distance travelled over the amount of time it took.  You can calculate this for the whole journey to calculate an average speed, or calculate it for different portions of the journey if there were different speeds.

### Time and Distance graphs

Distance is represented by the y axis, and time by the x axis.If an object is moving, the line is diagonal, because as time increases, the distance from the starting point increases too, giving a diagonal line.  The steeper this line, the faster the object is moving. For example, imagine Bob and John are walking to a shop that is 200m away. Bob takes 5 minutes, John takes only 3 minutes. So John has walked there faster. In the following diagram you cans see that the line representing John is steeper.

Remember, time never stops, so if an object is not moving, you will get a horizontal line, because the distance doesn't change, but time still goes on. This speed is 0, because it is not even moving

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