Ages 9 to 12 years. There are so many different kinds of energies; even the way we write, we talk we hear, we walk, needs some kind of energy to perform these actions. Not only the living things but the non-living things like machines and all require energy to perform the given work. The energy can be converted from one form to another while we perform all this actions. This encyclopedia will put a focus on the work, force and energy which exists and the cause and effects of these. The facts are well researched and presented with quality pictures for our young readers.