1. Energy: Forms and Changes
• The Nature of Energy
• Kinetic and Potential Energy
• Energy Conversions
• Conservation of Energy
• Physics and Energy

2. The Nature of Energy
• Energy can be defined as the ability to
do work.
• Energy is often measured in Joules (J).
• 1 Joule=1Kg-m2/sec2= 1 Nm
• Energy comes in many forms. The
main forms are: Mechanical, Heat,
Chemical, Electromagnetic, and
Nuclear.

3. The Nature of Energy
(continued)
• Mechanical energy is energy of motion.
• Examples include a moving car and
sound.
• Heat energy is energy of internal motion
(movement of atoms).
• Friction is one cause of heat energy.
• Chemical energy is stored in the bonds
that keep molecules together.

4. The Nature of Energy
(continued)
• Electromagnetic energy is caused by
moving charges.
• Examples include electricity and light.
• Nuclear energy is stored in the nucleus
of an atom.
• All stars (including our sun) run on
nuclear energy.

5. Kinetic and Potential Energy
• All of the types of energy just described
fit into one of two categories of energy:
Kinetic or Potential.
• Kinetic energy is the energy of motion.
• K.E.=(mass x velocity2)/2
• Kg x (m/sec)2=Kg-m2/sec2=Joule

6. Kinetic and Potential Energy
(continued)
• Potential energy is stored energy and is
sometimes called energy of position.
• For example, raising a bowling ball 1
meter above the ground gives it
potential energy relative to the ground.
• Gravitational Potential Energy (GPE)=
Weight x Height.
• Newtons x meters=Nm=Joule

7. Energy Conversions
• Energy can be converted from one form
to another.
• This process can happen over and over
again.
• For example, I can convert the
mechanical energy of rubbing my hands
together into heat energy.

8. Energy Conversions
(continued)
• One of the most common energy
conversions is Kinetic-Potential.
• For example, by holding a 20 Newton
bowling ball 1 meter above the ground,
it has 20 Joules of gravitational potential
energy.
• By releasing the bowling ball, its
potential energy is converted into
kinetic energy as it gains velocity.

9. Energy Conversions
(continued)
• As the bowling ball speeds up towards
the ground, its gravitational potential
energy is reduced, and its kinetic
energy is increased until the instant
before it hits the ground.
• At that point, the bowling ball has
converted all of its GPE into kinetic
energy, so that it now has 20 Joules of
kinetic energy.

10. Conservation of Energy
• The previous example shows how
energy is always conserved.
• In fact the Law of Conservation of
Energy says that energy can neither be
created nor destroyed by ordinary
means.
• Albert Einstein showed how energy can
be converted into mass and mass into
energy using his famous “E=mc2”

11. Conservation of Energy
(continued)
• The Law is consequently referred to as
“The Law of Conservation of
Mass-Energy.”

12. Physics and Energy
• Understanding energy is critical to
understanding the physical sciences.
• Everything we have studied in MFE
connects in some way to energy.
• For example, the faster you move, the
more momentum you have, the more
kinetic energy you have, the higher your
power, which means you consume
energy faster.