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## Section 1: Nature of Energy

Energy is everywhere around us, and it makes everything happen.  Every change that occurs, large or small, requires energy.  Energy can cause change and transfer from one form to another.  Our primary source of energy is the sun.  Light energy from the sun hits the earth and is used by plants.  Plants make food using light energy, which is chemical energy that plants and animals use.  Our bodies use energy so that we can move and grow.  There are many other forms of energy, including electrical, chemical, thermal, radiant, and nuclear energy.

Energy is often thought of as either energy that is moving or energy that is stored.  Kinetic energy is the energy something has when it is in motion.  The kinetic energy measure depends on a moving object’s mass and velocity.  Potential energy is energy that is stored, and it depends on an object’s position rather than its motion.  It means that the stored energy in an object has the potential to work or that the stored energy can be released.   Energy does not have to involve motion; even motionless objects can have stored or potential energy, meaning the object has the potential to cause change.

Energy can be stored in other ways as well.  For example, elastic potential energy can be stored in something that can be stretched or compressed, like a rubber band or a spring.  For example, a trampoline uses elastic potential energy.  The base of it that you jump on acts as a rubber band that bounces you upward.

Gravity is the pull of one object on another.  Gravitational potential energy is stored in an object due to its position and height.  The higher an object is in the air and the heavier it is, the more gravitational potential energy it has.  The gravitational potential energy is greatest at the highest point on a roller coaster.

Chemical potential energy is energy that is stored in chemical bonds.  It’s found in plants, batteries, food, coal, propane, and oil.

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Review:

1. List four types of energy.
2. Compare potential energy to kinetic energy.
3. Explain elastic potential energy.