[from Lorie Moffat]
Your son or daughter comes home from school with questions about energy. How do you begin to explain such a vast concept? Teaching kids about this subject starts with conveying that there are many forms of it around us and even inside us. Life as we know it would not exist without it. This force is so important that all food packages list Calories, an old energy unit. Energy is either stored or involved with motion.
The property of an object or a system (a group of objects) which enables it to do work is called energy. You need it to do work or to apply a force across a distance, meaning to move something. If it does involve moving an object, it is called kinetic. A ball rolling downhill has kinetic energy. It can also come from the position of an object or its arrangement. This type is called potential or stored energy. A ball that is stationary on the slope of a hill before it begins to roll down has what is known as gravitational potential energy. As the ball rolls downhill, the potential force it had is changed into kinetic. That is an example of the law of energy conservation; it cannot be created or destroyed, it changes form from one type to another.
Since it does change from one form to another, sometimes it is difficult to determine whether it is potential or kinetic. It can even be potential and kinetic simultaneously, such as thermal energy or heat. Even a moving object can have both potential and kinetic at the same time. As the ball rolls downhill, it changes from potential to kinetic. As it rolls, at any specific time, the total amount of force that the ball has does not change; the law of energy conservation holds. This type is considered mechanical energy.
When teaching kids about energy it’s important to relay that besides the motion of objects other types of kinetic energy include radiant, or light; radiant heat; acoustic, or sound; and electrical, or electricity through wires. Other types of potential energy include electrical energy stored in a battery, chemical, nuclear, magnetic, and solar; all stored in atoms or molecules. Elastic energy is potential energy within a fluid or solid that can be converted into mechanical.
Can there ever be a perpetual motion machine? That is, a machine that never stops moving and constantly creates its own energy as it works? Most machines noticeably heat up as they operate. This heat is from friction. The energy that goes into a machine is always greater than the amount of work it produces, because some of the initial energy changes into friction. Because friction is never completely eliminated, the energy going into a machine is always going to be larger than the machine’s output. A machine can never run indefinitely, so a perpetual motion machine cannot exist.
When teaching kids about energy you can explain the different types. It is either kinetic, involving motion, or potential, which is stored. It even changes form from one to another, leading to the law of energy conservation. It cannot be created or destroyed, it transforms from one type to another type. A perpetual motion machine cannot exist since such a device would counteract the law of energy conservation. Energy is a fascinating and vast subject but by remembering these basics, teaching kids about energy can be simple and fun.
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