In this lesson, we will proceed to graph of motion, where we will focus on the displacement-time graph, including analysis of the graph and solving some calculation questions.

There are 3 types of Motion Graph: the displacement-time graph, the velocity-time graph and the acceleration-time graph. All these graphs look similar. However, they are quite different, in terms of how they describe the motion. For example, in a displacement-time graph, the gradient is equal to the velocity while in a velocity-time graph, the gradient is equal to the acceleration.

Therefore, it is important for students to identify the type of graphs before analysing the graph.

In this lesson, we will focus on the displacement-time graph. The velocity-time graph and acceleration-time graph will be discussed in next lesson.

The displacement-time graph tells how the displacement of a moving object varies with time.

Let’s see the example above. This is a displacement-time graph illustrating the motion of 2 trolleys. We can tell the time and displacement of the trolleys easily from the graph. For example, at the time t = 2s, the displacement of trolley B is 1m, and the displacement of trolley A is 3m.

Another information we can gather from the graph is the velocity. In a displacement-time graph, the velocity of a motion is equal to the gradient of the graph: the higher the gradient, the higher the velocity. The lower the gradient, the lower the velocity.