Download Energy Powerpoint

Energy is used everyday… Can you
think of any examples?
Energy can take many forms
•
•
•
•
radiant
electrical
chemical
thermal
• nuclear
• sun
• power lines
• gas, food
• energy that comes from
the particles that make up
matter
• fission (reactor)
Traditionally, energy is defined as…
• the ability to do work or to cause something
to move.
• However, energy involves change, therefore
a better definition is:
• ENERGY = the ability to cause change.
• The basic unit of energy is the Joule (J).
• The equivalent units are : N*m
Kinetic Energy
• Kinetic energy is energy in the form of
motion.
• The amount of kinetic energy in a moving
object depends on its mass and velocity
• The formula for kinetic energy is :
• KE = ½ mv2
Kinetic Energy
energy of motion
All moving objects that
have mass have kinetic energy.
KE = 1/2
2
mv
m - mass of the object in kg
v - speed of the object in m/s
KE - the kinetic energy in J
Which of each pair has more
kinetic energy?
• a bus traveling at 65
mph?
• car traveling at 65
mph
• a bus traveling at 65
mph
• bus traveling at 40
mph
Potential Energy
• Potential Energy is stored energy.
• The amount of potential energy in a sample of
matter depends on its position or condition.
• Potential energy due to height above Earth’s
surface is called gravitational potential energy.
• Formula: PE (due to gravity) = mgh
9.8m/s2
Potential Energy
energy of position or condition
gravitational potential energy
PEg = mgh
m - mass of object in kg
g - acceleration of gravity in m/s2
h - height of object, in m,
from some arbitrary reference point
PE – gravitational potential energy in J
Circle which of each pair has
more potential energy:
• boy sitting in a tree 12
ft. in the air.
• squirrel sitting in a
tree 12 ft. in the air
• squirrel sitting in a
tree 30 feet in the air
• squirrel sitting in a
tree 12 ft in the air.
Click your mouse
to begin.
•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
Conservation of Energy
1. The law of conservation of energy states that
energy may change form, but it cannot be
created or destroyed under ordinary conditions.
2. Mechanical Energy is the total amount of
potential and kinetic energy in a system.
3. The amount of kinetic and potential energy in a
moving swing is always changing, whereas the
amount of mechanical energy is constant.
continued…
4. Let’s look at the case of a bouncing ball.
Energy changes from potential energy at
the top of the bounce to kinetic energy
when it hits the floor , and back to
potential energy as it goes back up. During
this time, the mechanical energy of the
ball stays constant.
5. Fill in the diagram of a bouncing ball
with the correct response below.
greatest potential energy,
no kinetic energy
kinetic energy decreasing,
potential energy increasing
greatest kinetic energy,
no potential energy
kinetic energy increasing,
potential energy decreasing
greatest kinetic energy,
no potential energy
6a. The ball in the previous diagram will eventually
stop bouncing. Why?
• Because gravity will slow the ball down .
6b. As the ball stops bouncing, is energy lost?
Explain.
• No, because the kinetic energy eventually
changes to potential energy, but energy is
not lost.
7a. In this picture, where does the roller
coaster have the most potential energy?
• At the top because it has
an instantaneous speed of
0 m/s.
7b. Where does it
have the most
kinetic energy?
• At the bottom because it’s
where it is going the
fastest.
References
1. http://www.hehs.d211.org/peopl
e/ruthek/PowerPoints/Conservati
on%20of%20Energy%2C%20Ene
rgy%2C%20and%20Work.ppt
2. faculty.physics.tamu.edu/ford/Po
werPoints/WorkEnergyPower.ppt
3. http://www.hazelwood.k12.mo.us/~cdavis01/ma
p2000/5th/eric03.ppt