Transcript kinetic energy

Energy
• What is energy?
• ENERGY is the ability to cause change.
• There are many different kinds of energy.
• Everything around us has energy – YOU have a
large amount of energy.
• When change occurs, energy is transferred
from one object to another.
– Footsteps transfer energy from foot to ground to
ears.
– Warmth is felt when the sunlight transfers energy
to a table or chair.
– Where do you see energy?
Energy of Motion
• KINETIC ENERGY is the energy an object has
due to its motion.
• KE = ½ x mass x (velocity)2
• The faster something is moving, the more
kinetic energy it has.
• The heavier a moving object is, the more
kinetic energy it has.
Which one has greater KE?
• Two vehicles, a semi and a VW
beetle, traveling at 60 mph each
• A snowball thrown or a
cannonball fired
• A bullet fired or a bowling ball
rolled down a lane
Energy of Position
• POTENTIAL ENERGY is the energy
an object has based on its
position.
• PE = mass * gravity * height
• Objects very high up have lots of
potential energy.
Which picture has greater PE?
YOU
Total Energy
• The TOTAL ENERGY is the combination of
kinetic and potential energy of a system.
• TE = KE + PE
• The LAW OF CONSERVATION OF ENERGY
states that energy can neither be created nor
destroyed – it only changes forms.
Practice!
• https://www.youtube.com/watch?v=izVeVfcfS
ws
• Where is Higgins’s potential energy the
greatest?
• What happens to his kinetic energy as he rolls
down the hill?
• Draw a picture of what Higgins’s path
might have looked like.
• What happens to Higgins’s potential
energy as he rolls down the hill?
• What happens to his total energy?
• At the very end, where does all the
energy from his motion go?
Phet demonstration
• We are going to look at an online
demonstration, and decide where potential
and kinetic energy are the highest.
– What is happening as the skateboarder goes
up/down the hill?
– What is happening to their total energy?
– What happens if we change the ramp?
• INTRO
– Using the U-shaped track, examine the
motion of the skater.
•
•
•
•
Is energy conserved?
Where is KE, PE the highest?
– Click on “Bar graph”
Notice where the skater’s speed is the highest
– Click on “Speed”
– How does this relate to KE? PE?
Notice where the skater’s height is the highest
– Click on “Grid”
– How does this relate to KE? PE?
• Friction
–Using the U-shaped track, examine
the motion of the skater.
• Is energy conserved?
• If you leave the skater alone, what
eventually happens?
–Click on “Speed”
• Where does this energy go?
–Click on “Bar graph”
Activity! – Human Continuum
• During this activity, you will be asked to stand
in an area of the room that represents your
answer to a question.
• You may be asked to defend your answer – be
ready to give your reasoning!
A skater starts at the top of a ramp. Is his energy:
Potential?
Kinetic?
Thermal?
A skater is at the bottom of the ramp, quickly
moving up to the other side. His energy is:
• Kinetic, potential, or a mix?
• Where is this skater on the ramp,
given his energy?
Top (moving up)
Bottom
Middle
Top (moving down)
Same question – where is
this skater?
Top
Middle
Bottom
Top
Middle
Bottom
• In which position does the skater
have the most…?
• Kinetic energy
• Potential energy
• Total energy
E
A
C
D
B
• At the highest point kinetic energy is
zero / maximum while the potential
energy is zero / maximum.
• At the lowest point kinetic energy is
zero / maximum while potential
energy is zero / maximum.
• Mass affects / does not affect the
amount of energy.
• As an object falls in gravity, kinetic
energy increases / decreases /
remains the same.
• As an object falls in gravity, potential
energy increases / decreases /
remains the same.
• As an object falls in gravity, total
energy increases / decreases /
remains the same.
• An object travelling faster and faster has a
kinetic energy that increases / decreases /
remains the same.
• An object travelling faster and faster has a
potential energy that increases / decreases /
remains the same.
• As an object speeds up, the total energy
increases / decreases / remains the same.
• As an object slows down, the total energy
increases / decreases / remains the same.