introduction to enery at least 2pages please tell fast
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ExplanationEnergy is a bit of a mystery. Most of the time we can't see it, yet it is everywhere around us. Revving car engines burn energy, hot cups of coffee hold energy, street lights that shine at night are using energy, sleeping dogs are using energy too—absolutely everything you can think of is using energy in one way or another. Energy is a magical thing that makes other things happen. Everything in the world is either energy or matter ("stuff" around us) and even matter, when you really get down to it, is a kind of energy!
Picture: A supernova is the remains of an exploding star and it's just about the most spectacular release of energy you can get. This particular one is a gigantic explosion of dusty gas 14 light-years across (roughly 132 billion kilometers) and booming outward at 2,000 km per second (or 4 million mph). Photo courtesy of NASA Jet Propulsion Laboratory (NASA-JPL):
Potential energy and kinetic energy
Although there are many kinds of energy in the world, they all fall into two broad categories: potential energy and kinetic energy. When energy is stored up and waiting to do things, we call it potential energy; "potential" simply means the energy has the ability to do something useful later on. When stored energy is being used to do something, we call it kinetic energy; "kinetic" means movement and, generally, when stored energy is being used up, it is making things move or happen.
It's easy to find examples of both potential energy and kinetic energy in the world around us. If you push a boulder up a hill, you'll find it's a real effort to get to the top. This is because the force of gravity is constantly trying to pull you (and the boulder) back down. In science, we say you have to do work against the force of gravity to push the boulder up the hill. Doing work means you have to use energy: the muscles in your body have to convert sugar and fat to make the energy you need to push the boulder. Where does this energy go? Although you use energy as you climb, your body and the boulder also gain energy—potential energy. When the boulder is at the top of the hill, you can let it go so it rolls back down again. It can roll down because it has stored potential energy. In other words, it has the potential to roll down the hill all by itself.
As the boulder starts to roll down the hill, the potential energy it had at the top is gradually converted into kinetic energy. When we talk about kinetic energy, we usually mean the energy something has because it is moving. Anything that has mass (contains some matter that takes up a volume) and moves along at a certain velocity (or speed) has kinetic energy. The more mass something has and the faster it goes (the higher the velocity), the more kinetic energy it has. If a truck and a car are driving parallel to one another down the freeway, at the same speed, the truck has more kinetic energy than the car because it has much more mass. (Read more about the science of motion.)