Energy - kendricknovak

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Transcript Energy - kendricknovak

Nature of Energy
• Energy is all around!
– Sound
– Light
– Wind
• You use energy when you:
– Hit a softball
– Lift your book
– Compress a spring
Nature of energy
• Living organisms need energy for growth &
• Energy is involved when
– A bird flies
– A bomb explodes
– Rain falls
– Electricity flows through a wire
Nature of energy
• What is energy that it can be involved in so
many different activities?
– Energy can be defined as the ability to do work
– If an object or organism does work (exerts a force
over a distance to move an object) the object or
organism uses energy
Nature of Energy
• Direct connection between energy and work
– Energy is measured in the same unit as work:
Joules (J)
• Objects gain energy because work is being
done on them
Forms of Energy
• 5 main categories
– Heat
– Chemical
– Electromagnetic
– Nuclear
– Mechanical
Heat Energy
• Internal motion of the atoms
– Moving particles produce heat
• Heat energy can be produced by friction
• Heat energy causes changes in temp. and
phase of any form of matter
Chemical Energy
• Required to bond atoms together
• When bonds are broken, energy is released
• Fuel and food are forms of stored chemical
How do you use energy?
Agenda for Thursday Nov 4th
1. Energy Notes
2. Movie
Electromagnetic Energy
• Power lines carry electromagnetic energy into
your home in the form of electricity
• Light is a form of electromagnetic energy
– Each color (ROY G BIV) is a different amount of
electromagnetic energy
• X-rays, radio waves, and lasers
Nuclear Energy
• Nucleus of an atom is the source of nuclear
• Fission (nucleus splits) – energy is released as
heat and light
• Fusion (nuclei joins) – energy is released
Nuclear Energy
• Sun’s energy is produced from a nuclear fusion
reaction in which hydrogen nuclei fuse to form
helium nuclei
• Nuclear energy is the most concentrated form of
Mechanical Energy
• When work is done to an object, it acquires
– Energy it acquires is known as mechanical energy
• When you kick a football, you give mechanical
energy to the football to make it move
– Give energy to a Bowling ball, ball hits pin and
they get energy
Energy Conversion
• Energy can be changed from one form to another
– Changes in the form of energy are called energy
• All energy forms can be converted to other forms
– Sun through solar cells to electricity
– Plants take sun energy to sugars (electromagnetic to
States of Energy
• Most common energy conversion is between
potential and kinetic energy
• All forms of energy can be in either of 2 states
– Potential
– Kinetic
Kinetic Energy
• Kinetic Energy – energy of motion
– Depends on mass and velocity
– Faster an object moves, more kinetic energy it has
– Greater the mass, more kinetic energy it has
• KE – 1/2mv2
• What has a greater affect of kinetic energy, mass
or velocity? Why?
Potential Energy
• Potential energy – stored energy
– Fuel, nucleus, food
– Stored because of the work done on it:
Stretching a rubber band
Winding a watch
Pulling back on a bow’s arrow
Lifting a brick high in the air
• Energy that is stored due to being stretched or
compressed is elastic potential energy
Gravitational Potential Energy
• Potential energy that is dependent on height
– Waterfall
– Suspension Bridge
– Falling snowflake
• GPE = weight x height
• GPE = mgh
Gravitational Potential Energy
• If you stand on a 3 meter diving board, you have 3
times the GPE than you had on a 1 meter diving board
Kinetic - Potential Energy Conversions
• Roller Coaster
– Mechanical energy brings them to the top
– This gives them great potential energy
– Conversion between potential to kinetic energy
powers cars through the entire ride
• At the point of max PE, the car has minimum KE
Kinetic - Potential Energy Conversions
• As a baseball
player throws the
ball into the air,
various energy
conversions take
Law of Conservation of Energy
• Energy cannot be created or destroyed
– It can only be converted from one form to another
• 1905, Albert Einstein said mass and energy
can be converted into each other
– Matter is destroyed, energy is created and vice
– E = mc2
What does the law of conservation
of energy state?
Agenda for Friday Nov 5th
1. Quiz
2. Finish Videos
3. KE/GPE Problem set
Which has more gravitational
potential energy: a ball on a 5 m
cliff or a ball on a 10 m cliff?
Agenda for Monday Nov 8th
1. Review GPE and KE
2. Lab
3. Problems on GE/KE
What is the equation for GE and
1. Go over labs
2. KE/GE problems