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 energy starts with conveying that there are many forms of energy around us and even inside us. Life as we know it would not exist without energy. Energy 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 energy to do work, or to apply a force across a distance, meaning to move something. If energy does involve moving an object, it is called kinetic energy. A ball rolling downhill has kinetic energy. Energy can also come from the position of an object or its arrangement. This type of energy is called potential energy, 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 energy it had is changed into kinetic energy. That is an example of the law of energy conservation; energy cannot be created or destroyed, it changes form from one type to another.
Since energy does change from one form to another, sometimes it is difficult to determine whether energy is potential or kinetic. Some energy is potential energy and kinetic energy simultaneously, such as thermal energy, or heat. Even a moving object can have both potential energy and kinetic energy at the same time. As the ball rolls downhill, its potential energy is changed into kinetic energy. As it rolls, at any specific time, the total amount of energy that the ball has does not change; the law of energy conservation holds. This type of energy 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 energy, or light; radiant heat energy; acoustic energy, or sound; and electrical energy, or electricity through wires. Other types of potential energy include electrical energy stored in a battery, chemical energy, nuclear energy, magnetic energy, and solar energy; all stored energy in atoms or molecules. Elastic energy is potential energy within a fluid or solid that can be converted into mechanical energy.
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 machines 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 of energy. Energy is either kinetic, involving motion, or potential, stored. Energy changes form from one to another, leading to the law of energy conservation. Energy 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 energy basics teaching kids about energy can be simple and fun.