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 & movement

• 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 energy

How do you use energy?

Agenda for Thursday Nov 4th 1.Energy Notes2.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 energy

• 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 energy

Mechanical Energy

• When work is done to an object, it acquires energy– 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

conversions

• All energy forms can be converted to other forms– Sun through solar cells to electricity– Plants take sun energy to sugars (electromagnetic to

chemical)

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 heightOr• 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 place

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

versa– E = mc2

What does the law of conservation of energy state?

Agenda for Friday Nov 5th 1.Quiz2.Finish Videos3.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 KE2.Lab3.Problems on GE/KE

What is the equation for GE and KE?

Agenda1.Go over labs2.KE/GE problems