Download ENERGY

ENERGY
THE DRIVING
FORCE
What is Energy?
• The ability to do work
• The ability to cause change
• Force is a push or pull
• Measured in Joules, Joules = kg●(m/s)2
• Formula: E = KE + PE
E = .5mv2 + magravh
(KE = .5 x mv2)
(PE
= magravh)
Energy is Conserved
(in a closed system)
• https://www.youtube.com/watch?v=p3msL1P8bw
Different Forms of Energy
• 6 different types:
• Mechanical
• Thermal Energy
• Chemical Energy
• Electrical Energy
• Electromagnetic Energy
• Nuclear Energy
Forms of Energy
• Mechanical Energy
• Describes energy stored and
released according to function or
force
Forms of Energy
• Thermal Energy
• Heat in all its forms and flows
Forms of Energy
• Chemical Energy
• Stored and released in the bonds
between atoms
Forms of Energy
• Electric Energy
• Energy that is caused by moving
electric charges
• Since the electric charges are moving,
this is a form of kinetic energy.
Forms of Energy
• Electromagnetic Energy
• Waves of mostly invisible energy
• Includes light, radio waves, X-rays
Forms of Energy
• Nuclear Energy
• Stored and released from the nucleus
of an atom
Two descriptions of Energy
• Potential Energy - Energy stored by
position or condition
• Kinetic Energy - Released energy or
energy of motion
Potential Energy
• The easiest quantified PE is
Gravitational PE
• This is the PE stored in an object by its
height above another reference point
• PEGrav = m agrav h
Joules = kg●(m/s)2
Remember, agrav = 9.8 m/s2
Potential Energy, revisited…
• Another form is Elastic PE
• This is the PE stored in an object by its
being disturbed from is natural state,
• and how much it wants to return to that
natural state
• Good examples:
• Springs, swings, pendulums, rubber
bands
Potential Energy, revisited…
• Another form is Chemical PE
• This is the PE stored in an object by the
chemical bonds between its atoms and
molecules
• The energy is released when the
chemicals react and form new bonds
• Good examples:
• Burning a log, firecrackers,
Kinetic Energy
• This is the KE released by an object by
its motion
• KE = ½ m v2
• Joules = kg●(m/s)2
Potential or Kinetic?
• On the next few slides, tell whether the
energy is potential or kinetic…
A bowling ball rolling down the
lane
1. Potential
2. Kinetic
A sandwich
1. Potential
2. Kinetic
A ball being thrown through the
air in a projectile path
1. Potential
2. Kinetic
A gallon of gasoline
1. Potential
2. Kinetic
A lawnmower burning a gallon of
gasoline
1. Potential
2. Kinetic
Law of Conservation of Energy
• Energy can not be created or destroyed
in normal reactions
• Energy can be changed from one form
to another
• The total amount of energy must be the
same before and after a change in
energy
Mechanical Energy in a Pendulum
Which of these describes Energy?
0%
0%
0%
0%
1.
2.
3.
4.
Ability to do work
Ability to cause change
Ability to increase energy
Ability to decrease work
At which point is PE at maximum?
0%
0%
0%
0%
1.
2.
3.
4.
A
B
C
D
Joules is not the unit for which of these?
0%
0%
0%
0%
1.
2.
3.
4.
Potential Energy
Kinetic Energy
Work
Force
At which point is KE at maximum?
0%
0%
0%
0%
1.
2.
3.
4.
A
B
C
D