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Energy
Kinetic and Potential Energy
What is Energy?
Remember: Work is done when
a force moves an object in the
same direction!
The ability to do work or cause
change is called energy.
Types of Energy
 Two basic kinds of energy are kinetic and
potential energy.
Kinetic
Potential
Kinetic
Potential
Kinetic Energy
The energy of motion
 Examples: car driving down the road, ball rolling down hill
Kinetic energy of an object depends on
both its mass and velocity (speed)
Kinetic energy increases as mass increases
Kinetic energy increases as speed increases
Potential Energy
Stored energy
 This type of energy has potential to do work
Examples: toy at the top of staircase, book on
bookshelf, apple on tree, stretched elastic)
2 types of potential energy:
gravitational potential energy
elastic potential energy
Elastic Potential Energy
That can be stretched or
compressed (squished)
Examples: rubber band,
bow and arrow, slinky,
trampoline
Gravitational Potential Energy
Energy based on height
Depends on height and weight
The more an object weighs the greater its
gravitational potential energy
The greater the object’s height, the greater its
gravitational potential energy
Energy Transformations
 Energy Transformations are when one
type of energy is changed into another
 The Law of the Conservation of Energy
states that energy cannot be created or
destroyed, but can be changed from one
object to another
 Objects can alternate between having
kinetic and potential energy, or can have
some of both at the same time.
Energy Transformations
One of the most common energy
transformations is the
transformation between potential
energy and kinetic energy.
Energy Transformations
When you lift the marble off the
ground it gets potential energy
because of its height.
Potential energy is greatest at the
highest point
Energy Transformations
 As the marble moves down,
Potential energy is converted into
kinetic energy
 Kinetic energy is greatest at the
lowest point
Energy Transformations
The marble slows down as it goes
uphill because kinetic energy is
being changed back into potential
energy.
Energy Transformation on a
Swing
0% Kinetic
At the top of the swing,
you have all potential
100% Potential
energy, as you swing down
you change your PE into
kinetic energy. At the
bottom of the swing you
have all KE. As you go
back up KE goes back to
PE
100 % Kinetic
0% Potential
Energy Transformations with a
falling object
Energy Transformation on a
Roller Coaster
Energy Transformations
100%
Potential
100%
Potential
50%
potential,
50%
kinetic
100%
Kinetic
50%
potential,
50%
kinetic