Video: Pack 3 • Paper 3 • Question 14

Pack 3 • Paper 3 • Question 14

01:31

Video Transcript

The distance–time graph shows the first 70 seconds of a cyclist’s journey. Between which two times is the cyclist stationary? Explain your answer.

If the cyclist is stationary, then this means that they are not moving. So no distance will be covered. This section of the distance–time graph will be flat as the distance will not be changing. Looking at the graph, we can see that the line is flat in one place, between 30 and 40 seconds.

To explain our answer, we can say that the gradient of the line is zero at this point. So no distance is travelled. If we recall as well that speed is equal to distance divided by time, then if the distance travelled is zero, the speed will also be zero. And if the speed is zero, then the cyclist is stationary.

Work out the speed of the bike between zero and 30 seconds. To calculate the speed of the bike during the first 30 seconds, we need to know both the distance travelled and the time taken. Reading from the vertical axis, we see that the distance travelled is 200 metres. And reading from the horizontal axis, the time taken is 30 seconds. So our calculation for the speed is 200 metres divided by 30 seconds.

We can simplify this fraction by cancelling a factor of 10 from both the numerator and the denominator. The speed of the bike between zero and 30 seconds is 20 over three metres per second.

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