(EGY) Energy Transformations Lesson

Energy Transformations

All objects have energy. The word energy comes from the Greek word, energeia, meaning activity or operation.  In physical science, energy can be defined as the ability to do work. Energy is also measured in the same units work is measured, joules. Everything we do involves energy.  Getting up, going to school, and doing activities require energy. In fact, everything that happens in the universe, from the eruption of volcanoes to the sprouting of seeds, to the moving of people, takes energy. When we turn on a motor, drive a car, cook on a stove or switch on a light, we are using energy.

The following video, A Guide to the Energy of the Earth, provides an excellent concise summary of what we will be learning in this module. As you watch the video below, be sure to listen for descriptions of different forms of energy, what happens to energy, various sources of energy, and more.

All energy can be classified as either potential energy or kinetic energy. Energy is continually being transferred from potential energy to kinetic energy and vice versa. Potential energy is stored energy.  It can also be viewed as energy waiting to happen. Just because an object is not moving doesn't mean it doesn't have energy.

Let's think about this rock on the edge of a cliff. Do you think it has energy? Would you want to stand on the ground below this rock? Remember that energy is the ability to do work.  This rock certainly has the ability to do work even though there is currently no work being done. This is a great example of potential energy.  There are different kinds of potential energy: gravitational potential energy, elastic potential energy, chemical potential energy, electrical potential energy, and more.

Let's look at a couple of different kinds of potential energy.   First, let's explore gravitational potential energy.   The rock hanging on the cliff has a form of stored energy called gravitational potential energy. This form of energy is due to the downward pull of Earth's gravity. Gravitational potential energy depends on an object's mass and its height above the ground.     The higher an object is above the ground or the greater its mass, the more gravitational potential energy it has. For example, the hanging rock on the cliff would cause even more damage if it fell from a greater height. More damage also would be caused if a rock with more mass fell from the same height. The gravitational potential energy of an object increases if its mass or height above the ground increases.

Another kind of potential energy is elastic potential energy. To understand elastic potential energy, think about a rubber band. If you stretch a rubber band it has elastic potential energy because the energy is stored as the band object is stretched. The more you stretch, the more elastic potential energy it has. This stored energy then can cause the rubber band to fly across the room when you let it go. Looking at a spring is another example. A spring has two ways that it can store elastic potential energy. If the spring is squeezed together, or compressed, it has a tendency to change back to its rest length. The spring also will return to its rest length if it is stretched. Either by compression or stretching, stored elastic potential energy gives an object the ability to change.

Lastly, eating provides an example of the last type of potential energy, chemical potential energy. Chemical potential energy is the energy stored in bonds between the atoms that make up matter. Chemical potential energy can be released during chemical reactions when these bonds are broken. You gain energy by eating because food contains chemical potential energy. Fossil fuels, such as oil and coal, are energy sources because they contain chemical potential energy. Once the bonds of the atoms in food or in fossil fuels are broken, the energy is released and made useful in the form of kinetic energy.

Kinetic energy is working energy. It's the energy an object has due to its motion. As you can imagine there are many kinds of kinetic energy:  vibrational, mechanical, rotational, electrical, and more.  

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