Observe the image below and describe where you
would find Potential Energy on a roller coaster.
• Then describe what you think “Potential Energy
Means”
Potential Energy
• Potential energy is the same as
stored energy.
• When you lift a heavy object you
exert energy which later will
become kinetic energy when the
object is dropped.
• A lift motor from a roller coaster
exerts potential energy when lifting
the train to the top of the hill. The
higher the train is lifted by the
motor the more potential energy is
produced; thus, forming a greater
amount of kinetic energy when the
train is dropped.
• At the top of the hills the train has
a huge amount of potential energy,
but it has very little kinetic energy.
Types of Potential Energy
• An object that rises or falls experiences a change in its kinetic and
gravitational potential energy.
• When you stretch a rubber band you give it elastic potential energy.
• There is only one kind of kinetic energy.
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Potential Energy
• Potential energy that depends on
gravity is gravitational potential
energy.
• Gravity cannot be affected or
changed, because we live on Earth
and gravity is constant (9.8 m/s).
• So engineers can only control two
aspects to control how much PE a
roller coaster has: mass and height.
• Gravitational Potential Energy =
mass x gravity x height
• GPE = mgh
Example 1
• Suppose a hiker climbs 40
meters up a hill and has a mass
of 70 kg. How many joules of
gravitational potential energy
has the hiker gained at the top
of the climb?
• MUST show your work!
• GPE = mgh
• GPE = 70 kg x 9.8 m/s x 40 m
• GPE = 27,440 J
Example 2
• What is the potential energy of a
rock that has a mass of 10 kg
that is sitting on top of a hill that
is 40 meters high.
• MUST show your work.
• GPE = mgh
• GPE = 10 kg x 9.8 m/s x 40 m
• GPE = 3,920 J
Potential Energy
• The greater the mass of an object or the greater the height it is lifted,
the greater its gravitational potential energy.