Download Kinetic and Potential Energy - Cinnaminson Township Public

Kinetic and Potential
Energy
After the Lesson:
• You will be able to define and identify
Kinetic and Potential energy.
• You will be able to give examples of the
two forms of energy.
• You will be able to explain how one can
transfer to the other.
Definition of Energy…
The ability or capacity to do work.
Measured by the capability of doing work:
potential energy
or
the conversion of this capability to motion:
kinetic energy.
Kinetic Energy
Potential Energy
Radiant
Thermal
Electrical
Chemical
Mechanical
Nuclear
Sound
Magnetic
Potential Energy…
• Energy due to position or stored
energy.
Potential energy is calculated by:
The object’s weight, multiplied by the earth's gravitational pull (9.8 m/sec
sq), multiplied by the distance the object can fall.
POTENTIAL ENERGY
Potential energy exists whenever an object which has mass
has a position within a force field. The most everyday
example of this is the position of objects in the earth's
gravitational field. The potential energy of an object in this
case is given by the relation:
PE = mgh
PE = Energy (in Joules)
m = mass (in kilograms)
g = gravitational acceleration of the earth (9.8 m/sec2)
h = height above earth's surface (in meters)
Examples of Potential Energy:
Stretching a rubber band..
-Stores energy
Water at the top of a waterfall..
-Stores energy
Yo–Yo in held in your hand..
-Stores energy because of position
Drawing a Bow…
-Stores energy because of position
• When the position of an object is
altered it, creates Potential Energy.
• A yo-yo on the table, doesn’t have energy,
but when picked up, it alters its position
and now it has the ability (or potential) to
do work.
• A bow doesn’t have the capacity to do
work, unless it’s held at an elevated
position.
Definition of Kinetic Energy…
The energy of motion.
Kinetic energy is calculated by one half of the object’s mass,
multiplied by the object’s speed- squared.
KINETIC ENERGY
The greater the mass or velocity of a moving object, the
more kinetic energy it has.
Kinetic Energy Lab
Examples of Kinetic Energy…
• Shooting a rubber
band.
• Water falling over
the fall.
• A Yo-Yo in motion.
• Releasing the arrow
from the bow.
Potential Energy Converted
to Kinetic Energy…
When stored energy begins to move,
the object now transfers from
potential energy into kinetic energy.
Standing still
Running
What happens
when the cord
is cut?
Potential energy
is converted to
kinetic energy!
• Potential Energy– “stored” energy
– related to an object’s height
above the ground
– the higher something is, the more
potential energy it has
• Kinetic Energy– “energy of motion”
– related to an object’s velocity
– the faster something is traveling,
the more kinetic energy it has
•Decide whether each slide is an
example of potential or kinetic energy.
•Click on your answer to see if you are
correct.
Whenever you see this picture, you will
need to write the answer in your journal.
Potential
Energy
Kinetic
Energy
Potential
Energy
Kinetic
Energy
Potential
Energy
Kinetic
Energy
Potential
Energy
Kinetic
Energy
Potential
Energy
Kinetic
Energy
Potential
Energy
Kinetic
Energy
Potential
Energy
Kinetic
Energy
Potential
Energy
Kinetic
Energy
Potential
Energy
Kinetic
Energy
Potential
Energy
Kinetic
Energy
• Conservation of energy says that the
amount of energy the coaster has will
always be constant. This means the
potential energy of the car plus the
kinetic energy of the car must always be
the same. If the potential goes up, the
kinetic must come down; if the kinetic
goes up, the potential must come down.
The Hill: Conservation of
Energy
Why is the first hill of the
roller coaster always the
highest?
At the top of the first hill:
• Kinetic Energy?
– The coaster’s velocity is zero . . .
– Kinetic energy = 0
• Potential Energy?
– The coaster is very high . . .
– Potential energy = high
• All of the coaster’s energy is in the
form of potential energy.
At the bottom of the hill:
• Kinetic Energy?
– The coaster is moving at a high
velocity.
– Kinetic energy = high
• Potential Energy?
– The height of the coaster is zero . . .
– Potential energy = 0
• By the time the coaster reaches the
bottom of the hill, all potential energy
has been transformed to kinetic energy.
But why is the first hill
highest?
• When the coaster reaches the bottom of the
first hill, all its energy has been transformed
from potential to kinetic energy.
• As it goes up the next hill, that kinetic energy
must be transformed back into potential
energy so the process can repeat.
• But don’t forget friction – the coaster is always
losing energy to friction between the car and
the tracks, so each time it goes up a hill it will
have less kinetic energy to transform back into
potential.
The first hill of a roller coaster always
must be the highest, otherwise the
coaster won’t have enough energy to get
up the other hills.