Andrea T. Bailey
What is Energy?
You use energy all the time. When you turn on a light or ride in a vehicle, you use energy. It took energy to make the books that you read, to power the computer that you use and the video games that you play. A lot of energy we use comes from oil and coal. Oil and coal are fossil fuels. They are made inside the earth from dead plants and animals.
Fossil fuels have powered many of the gains we have made during the last two hundred years, although fossil fuels produce a lot of pollution. Sooner or later, they will run out. These types of energy sources are called nonrenewable. Scientists are searching for other ways to replace fossil fuels.
Energy sources such as energy from the sun, wind, waves and Earth's internal heat can never be used up. These types of energy sources are called renewable. And because these renewable energy sources don't burn anything, they don't add to global warming. These types of energy sources are call renewable.
Energy can be defined as the capacity to do work. Work is defined as any interaction in a system with its surroundings that can affect an outcome (1). The nature of energy is very complex, but it is best described by these characteristics in kid friendly terms:
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energy is the ability to do work
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work is the application of force through a distance (e.g., carrying yourself and a loaded backpack up three flights of stairs)
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force is that which can stop or start matter already moving (e.g., you are stopped in the lunch line and someone is talking to a friend and doesn't see you standing in front of them, and can't stop walking before colliding into you, pushing you out of the lunch line.)
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motion is a change in distance or direction with time
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Energy cannot be created or destroyed but it can be converted from one form to another. Everything that occurs in our universe revolves around energy. Energy comes in many different forms such as heat, light, sound and electricity. There are two major categories of energy: kinetic and potential energy. If the energy is moving or is in use, it is called kinetic energy. An example of kinetic energy is a car rolling down a hill. If the energy is due to the position or composition of an object, it is called potential energy. An example of potential energy is a car parked on a hill (due to its position). Therefore, Energy is anything that can do Work or cause a change.
The unit of measurement of work combines the unit of force, Newton, with the unit of distance, meter and the resulting unit of work is the Newton-meter. One joule of work is done when a force of 1 N is exerted to move an object through a distance of 1 m. According to Hewitt (1997), James Joule was able to show 1 joule is equal to 4184 Calories (2).
The rate at which work is done is called Power and can be calculated by dividing work by time. The unit of power is named Watt (W) named after the inventor of the first practical steam engine James Watt.
Watt measured the power of his machines by how fast his horses could do work so that people of his era during the 1700's could understand them. Watt's observations showed him that a horse could lift 550 pounds to a height of 1 foot in one second. That rate of doing work is known as a horsepower (HP) and is still used today as a standard measurement in the United States.
A 100 Watt light bulb uses energy at a rate that could move an object with force of 100 N over a distance of 1 m each second. If you run a 60 watt bulb for an hour it brings an awful lot of energy into your house. The amount of electrical energy used over a period of time is measured in a unit called watt. We can use the watt to compare the rates at which different electrical devices use energy. Electric companies or energy companies provide us with a lot of energy for a pretty reasonable price. These companies are converting (changing) chemical energy in coal, oil, gas or nuclear energy into electrical energy for consumers to use as light, heat, or some sort of energy.