Stored energy
Many of the objects around you have stored energy or potential energy. Petrol in a car's fuel tank and books on a shelf both have potential energy. They are not using energy at the moment but have stored energy. Stored energy gives objects the potential to make things happen: the books can fall off the shelf and the petrol can burn.
One form of potential energy is the chemical energy your body gains from eating food. This energy enables you to run, play sport, heat your body and keep your heart beating. The foods that you eat originally obtained energy from the Sun. Plants capture light from the Sun and convert it into chemical energy in the form of simple sugars. This happens in a process called photosynthesis. When you eat plants, their seeds, nuts or grains (or eat animals that have eaten them), your body uses the chemical energy from these simple sugars and starch as your energy source.
Forms of Stored Energy
- Gravitational potential energy is energy stored in an object when it is above the ground. The greater the height, the more gravitational potential energy an object has. For example, the higher a water slide, the more gravitational potential energy you have at the top and the more kinetic energy (speed) you will have on the way down!
- Chemical energy is energy stored in substances. This energy is released by your body when you digest food, and by cars when fuel is burnt. Wood, paper, apples, petrol and batteries all contain chemical energy.
- Elastic potential energy is energy stored in a stretched or squashed spring. Stretched rubber bands also store elastic potential energy, which is released when they are let go.
- Nuclear energy is energy stored inside the tiny atoms that make up all matter. Nuclear energy is released in a nuclear power plant, when a nuclear bomb explodes, and inside the Sun. Nuclear reactions produce heat and light.