A **distance-time graph** tells us how far an object has moved with time.

If an object moves along a straight line, the distance travelled can be represented by a distance-time graph. In a distance-time graph, the **gradient** of the line is equal to the speed of the object.

Speed is the time rate at which an object is moving along a path, while velocity is the rate and direction of an object's movement. **Velocity is a vector quantity **because it has both a magnitude and an associated direction. To calculate velocity, displacement is used in calculations, rather than distance. **Displacement is also a vector quantity** as it not only gives the distance travelled but also the direction of the distance travelled.

**Acceleration is the rate of change of velocity**. Usually, acceleration means the speed is changing, but not always. When an object moves in a circular path at a constant speed, it is still accelerating, because the direction of its velocity is changing.

**Velocity time graph** gives us the idea of acceleration and displacement.

Acceleration can be calculated by dividing the change in velocity (measured in metres per second) by the time taken for the change (in seconds). The units of acceleration are m/s^{2}.

Acceleration can also be calculated by finding the gradient of the line in the graph.

The **area** under the line in a velocity-time graph represents the **distance **travelled.