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## What is energy?

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### What is energy? – PowerPoint PPT presentation

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Title: What is energy?

1
What is energy?
2
WHAT IS ENERGY?
• Energy is the ability to do work.
• Work is done when a force causes an object to
move in the direction of the force. Work is a
transfer of energy.
• Energy and work are expressed in units of joules
(J).

3
WHAT IS ENERGY?
4
Kinetic Energy
• Kinetic energy is the energy of motion. All
moving objects have kinetic energy.
• Kinetic Energy Depends on Mass and Speed If you
know an objects mass (m) and its speed (v), you
can calculate the objects kinetic energy with
the following equation

5
Potential Energy
• Potential energy is the energy an object has
because of its position.
• Gravitational Potential Energy The amount of
gravitational potential energy that an object has
depends on its weight and its height.
• gravitational potential energy ? weight ? height

6
Mechanical Energy
• Mechanical energy is the total energy of motion
and position of an object. Both kinetic energy
and potential energy are kinds of mechanical
energy.
• The equation to find mechanical energy is
• mechanical energy ? potential energy ? kinetic
energy

7
Mechanical Energy
• The mechanical energy of an object remains the
same unless it transfers some energy to another
object.
• But even if the mechanical energy of an object
stays the same, the potential energy or kinetic
energy can increase or decrease.

8
Other Forms of Energy
• Thermal Energy is all of the kinetic energy due
to random motion of the particles that make up an
object.
• All matter is made up of particles that are
always in random motion. So, all matter has
thermal energy.
• Thermal energy increases as temperature
increases and increases as the number of
particles increases.

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10
Other Forms of Energy
• Chemical Energy is the energy of a chemical
compound that changes as its atoms are
rearranged.
• Chemical energy is a form of potential energy
because it depends on the position and
arrangement of the atoms in a compound.
• The energy in food is chemical energy.

11
Other Forms of Energy
• Electrical Energy is the energy of moving
electrons. Electrical energy can be thought of as
potential energy that is used when you plug in an
electrical appliance and use it.
• Sound Energy is caused by an objects
vibrations. The objects vibrations transmit some
kinetic energy to the air particles, which also
vibrate. These vibrations transmit sound energy.

12
Other Forms of Energy
• Light Energy is produced by the vibrations of
electrically charged particles.
• Nuclear Energy is energy that comes from changes
in the nucleus of an atom. Nuclear energy can be
produced when nuclei are joined in a fusion
reaction or when a nucleus is split apart in a
fission reaction.

13
Other Forms of Energy
• Solar energy is the radiant light and heat from
the Sun. It is a renewable energy. It is used as
solar power to provide electrical generation.
• Geothermal energy originates from the original
formation of the planet, from radioactive decay
of minerals, and from solar energy absorbed at
the surface. It is power extracted from heat
stored in the Earth.

14
Kinetic Energy and Potential Energy
• An energy conversion is a change from one form of
energy to another. Any form of energy can change
into any other form of energy.
• As the skateboarder on the next slide travels up
and down the half-pipe, his energy changes back
and forth between kinetic energy and potential
energy.

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16
Kinetic Energy and Potential Energy
• Elastic Potential Energy Stretching a rubber
band stores elastic potential energy in the
rubber band.
• When you let the rubber band go, it goes back to
its original shape. It releases its stored-up
potential energy as it does so.

17
Conversions Involving Chemical Energy
• Chemical energy is stored in the food you eat.
Your body uses this chemical energy to function.
• Energy Conversion in Plants The chemical energy
in the food you eat comes from the suns energy.
Plants use photosynthesis to convert light energy
into chemical energy, as shown on the next slide.

18
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19
Conversions Involving Chemical Energy
• The Process Continues Plants change light energy
into chemical energy. The chemical energy in the
food you eat is changed into another kind of
chemical energy that your body can use.
• Your body then uses that energy to give you
kinetic energy that you use in everything you do.

20
Why Energy Conversions Are Important?
• Energy conversions are needed for everything we
do. Heating our homes, getting energy from a
meal, and many other things use energy
conversions.
• Machines, such as a hair dryer, help harness
energy and make that energy work for you.

21
Why Energy Conversions Are Important?
• Conversions Involving Electrical Energy Some
common energy conversions that involve electrical
energy are shown in the table below.

Alarm clock electrical energy ? light and sound energy
Battery chemical energy ? electrical energy
Light bulb electrical energy ? light and thermal energy
Blender electrical energy ? kinetic and sound energy
22
Energy and Machines
• A machine can make work easier by changing the
size or direction (or both) of the force needed
to do the work. Some machines allow you to use
less force over a greater distance to do the same
amount of work.
• Machines as Energy Converters Some machines