If possible, it would be great to introduce the class to these ideas using a sensor, which gives an output on a distance/time graph by recording how far an object is from the sensor. (It can also be linked to a computer so that the display can be viewed easily by all.)
The idea of this problem is to introduce children to interpreting distance/time graphs and it will be invaluable to allow the class plenty of time to explore what the interactivity does. It may be appropriate to invite pupils to try and replicate the first graph on an interactive whiteboard so that everyone can see. Discussing the properties of this first graph all together will help the children
to continue the problem for themselves. You may like to try Take Your Dog for a Walk
after this problem.