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Energy
The ability to do work
 Work is done when a force moves an
object over a distance

Potential Energy

Stored energy an object has due to its
position.
– Ex: A rock on top of a cliff has potential
energy because of its position above
ground level
– Ex: A lump of coal contains potential
energy in its chemical bonds, causing fire
when exposed to a flame
Kinetic Energy

Energy of motion
– Ex: A rock falling off a cliff
– The heat given off by a burning lump of
coal
– The faster an object moves, the more
kinetic energy it has
Energy

Potential energy may be changed into
kinetic energy when an object begins
to move
– Ex: Water held back by a dam has
potential energy but no kinetic energy.
Releasing the water and letting it flow
changes its potential energy into kinetic
energy.
Energy

Kinetic energy may also be changed into
potential energy
– Ex: When a ball is thrown straight up in the air,
its kinetic energy changes into potential energy
as the ball rises higher above the ground. At the
highest point, the ball is motionless and has only
potential energy. As the ball falls back to the
ground, the potential energy changes back into
kinetic energy.
Forms of Energy

There are 6 forms of energy
– Mechanical
– Chemical
– Nuclear
– Heat (thermal)
– Electric
– Light (radiant, electromagnetic)
Mechanical Energy

Energy with which moving objects
perform work
– Ex: hammer striking a nail, a jack lifting a
car, pedals turning the wheel of a bike
– Sound is a type of mechanical energy
Chemical energy

Energy stored in certain substances
because of the make up of their
chemical bonds
– Ex: coal, oil, natural gas, food
Nuclear energy

Energy stored within the nucleus of an
atom
– Joining small nuclei together or splitting
large nuclei apart
Heat Energy

Produced by the molecular motion of
matter
– Ex: rubbing your hands together, cellular
respiration, burning fuel oil in a home
Electric Energy

Produced by the flow of electrons
through a conductor, such as a wire.
– Ex: computers, light bulbs, washing
machines all are operated with electric
energy.
– A generator produces electric energy.
Light Energy

Form of radiant energy that moves in
waves
– Ex: magnifying glass burns a hole in a
leaf or using a laser beam to burn a hole
in a steel plate.
Conservation of Energy
The law of conservation of energy
states that energy can neither be
created nor destroyed.
 Energy can easily be transformed from
one type of energy into another type of
energy

Conservation of Matter

The law of conservation of matter
states that matter can neither be
created or destroyed. Energy and
matter are interchangeable. The total
amount of energy and matter in the
universe is constant and each can be
converted into the other.
– Ex: The sun converts large amounts of
matter into light and heat energy
Energy
Transformations



Ex: when you take a bus to school, chemical
energy in the gas is changed into
mechanical energy that turns the wheels of
the bus
Ex: The bell rings between classes, electric
energy is transformed into sound energy
Ex: At night when you are reading, electric
energy is changed into light energy
Unusable Energy

During energy transformation heat
energy is produced that is not usable.
– A cars motor changes chemical energy in
gas into mechanical energy to move the
car. The motor eventually becomes hot
due to the burning of fuel and friction of
the motors moving parts rubbing against
one another
Unusable Energy

Ex: a vacuum cleaner contains a motor
that transforms electric energy into
mechanical energy. Run a vacuum
cleaner for a few minutes and it gets
warm. The electric energy entering
the motor produced mechanical
energy to operate the appliance and
an unusable amount of heat energy.