Look at the diagram on the main screen. This shows a car being moved forwards by an elastic band.

To do this you need a sheet of wood with two screws fastened in it. Ask an adult to do this for you.

Now stretch an elastic band between the screws and then place a model car or something else with wheels against the band.

Use the car to pull the band longer, as shown, then let it go.

Does the car go further if you pull the band more before you let it go? Think of a way of testing this.