Energy in simple activities

Your book shows energy at work with three simple activities. Here is what each one shows.

The balloon: blow up a balloon, hold its mouth tight, then let go. Air rushes out of the balloon and pushes the balloon forward. So moving air can make things move. (If the balloon is taped to a straw on a string, it zooms along the string like a rocket.)

The rubber-band guitar: stretch rubber bands round a cardboard box, across a hole, and pluck them. Plucking makes the bands vibrate — shake quickly to and fro — and they make sounds. This is sound energy.

The sun-powered water warmer: fill two cups with water. Keep one in sunlight and one in the shade for 15 to 20 minutes. The water kept in the sunlight is warmer, because the Sun heats it up. This shows that sunlight gives us heat energy.