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Chapter 9 Energy and Energy Resources

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Chapter 9 Energy and Energy Resources Section 1 What is Energy? Energy and Work- Working together What is energy? Energy is the ability to do work What is work? – PowerPoint PPT presentation

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Title: Chapter 9 Energy and Energy Resources


1
Chapter 9Energy and Energy Resources
  • Section 1
  • What is Energy?

2
Energy and Work- Working together
  • What is energy?
  • Energy is the ability to do work
  • What is work?
  • Work occurs when a force causes an object to move
    in the direction of the force. (Work transfers
    energy)

3
Kinetic Energy is Energy of Motion
  • An object which has motion-whether it be vertical
    or horizontal motion- has kinetic energy (KE)
  • Three forms of KE are vibrational, rotational,
    and translational
  • To keep it simple, we will focus on translational
    KE or the energy due to motion from one location
    to another

4
Potential Energy Is Energy of Position
  • Potential energy is the energy an object has
    because of its position or shape.

5
Potential Energy Is Energy of Position
  • When in their resting position, they have no
    energy. The potential energy comes from the
    change in shape or position from its usual shape

6
Potential Energy Is Energy of Position
  • A rubber band is another good example of
    potential energy.

No energy
potential energy
7
  • Gravitational potential energy is the energy
    stored in an object as the result of its vertical
    position or height.
  • The gravitational potential energy of the massive
    ball of a demolition machine is dependent on two
    variables - the mass of the ball and the height
    to which it is raised.

8
  • There is a direct relation between gravitational
    potential energy and the mass of an object.
  • More massive objects have greater gravitational
    potential energy.
  • There is also a direct relation between
    gravitational potential energy and the height of
    an object.
  • The higher that an object is elevated, the
    greater the gravitational potential energy.

9
To determine the gravitational potential energy
of an object, a zero height position must first
be arbitrarily assigned. Typically, the ground is
considered to be a position of zero height. In
the lab, the desk could be zero height.
Since the gravitational potential energy of an
object is directly proportional to its height
above the zero position, a doubling of the height
will result in a doubling of the gravitational
potential energy. A tripling of the height will
result in a tripling of the gravitational
potential energy.
10
Forms of Energy Thermal Energy
  • All energy involves either motion or position
  • Thermal energy all particles of matter are in
    constant motion so they have kinetic energy.
    Particles also have energy because of molecular
    arrangement
  • Thermal energy is the total energy of the
    particles that make up an object

11
Forms of Energy Chemical Energy
  • Chemical energy is the energy of a compound that
    changes as its atoms are rearranged to form new
    compounds
  • Chemical energy is a form of potential energy
  • When compounds, like sugar in some foods are
    formed, work is done to bond the atoms to form
    molecules

12
Forms of EnergyElectrical Energy
  • Electrical Energy is the energy of moving
    electrons
  • When an electric appliance is plugged in to an
    outlet, the electrons in the wires move back and
    forth transferring energy and producing the work
    of the stereo which is to produce sound.
  • Electrical energy can be a form of potential
    energy

13
Forms of EnergySound Energy
  • Sound is created by the movement of air past the
    vocal cords making them vibrate
  • Sound energy is caused by an objects vibrations
  • Sound energy is a form of potential and kinetic
    energy

14
Forms of EnergyLight Energy
  • Light energy is produced by the vibrations of
    electrically charged particles

15
Forms of EnergyNuclear Energy
  • Nuclear energy is formed by fusing nuclei or
    splitting them
  • fusion or fission

16
Energy and Machines
  • You transfer energy to the nutcracker and it
    transfers energy to the walnut
  • The nutcracker will not transfer more energy to
    the walnut than you transfer to the nutcracker

17
Energy and Machines
  • Machines are energy converters
  • When machines transfer energy, energy conversions
    can often result

18
Lets summarize
  • What determines an objects thermal energy?

An objects thermal energy depends on its
temperature, the arrangement of its particles,
and the number of particles in the object
19
Lets summarize
  • Describe why chemical energy is a form of
    potential energy.

When a substance forms, work is done to bond
particles of matter together. The energy that
creates the new bonds is stored in the substance
as potential energy
20
Lets summarize
  • When you hit a nail into a board using a hammer,
    the head of the nail gets warm. IN TERMS OF
    KINETIC AND POTENTIAL ENERGY, DESCRIBE WHY THIS
    HAPPENS.

The kinetic energy of the moving hammer is
transferred to the head of the nail, causing
particle sin the nail to move faster. The faster
the particles move, the greater their thermal
energy.
21
EQ 1 Explain the relationship between energy
and work
  • Energy is the ability to do work. Work cannot
    occur without energy

22
Lets Review
When you bounce a basketball, you give it kinetic
energy. At the moment the ball hits the ground,
its kinetic, its kinetic energy energy is
greatest and its potential energy is zero. At
that moment, the change in the shape that occurs
when it hits the ground gives the ball potential
energy that is used when the ball moves back
upward. When the ball bounces back up toward
your hand , its kinetic energy is converted into
potential energy because the position changes.
At the moment the ball is at the top of its
bounce, its kinetic energy is zero.
23
Why energy conversions are important
  • They make energy useful by converting energy to a
    form of energy we can use
  • Energy efficiency is a comparison to the amount
    of energy before a conversion with the amount of
    useful energy after a conversionefficiency means
    less waste
  • Work input is always greater than work output

24
Baseball hitting a bat
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