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What is energy?


What is energy? – PowerPoint PPT presentation

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Title: What is energy?

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

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

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

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
  • The equation to find mechanical energy is
  • mechanical energy ? potential energy ? kinetic

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

Other Forms of Energy
  • Thermal Energy is all of the kinetic energy due
    to random motion of the particles that make up an
  • 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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Other Forms of Energy
  • Chemical Energy is the energy of a chemical
    compound that changes as its atoms are
  • 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.

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.

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.

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.

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

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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.

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.

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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.

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
  • Machines, such as a hair dryer, help harness
    energy and make that energy work for you.

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
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
    help you use energy by converting it into the
    form of energy that you need.

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