Who’s doing work?

Work is only done by a force on an object if the force causes the object to move in the direction of the force. Objects that are at rest may have many forces acting on them, but no work is done if there is no movement.

W = F·d Work, the product of the force exerted on an object and the distance the object moves in the direction of the force. W = F·d

the time rate of doing work; or the time rate transfer of energy. Power, by definition, is the time rate of doing work; or the time rate transfer of energy. P = W / t

P = W / t work over time. My friend, Power, has been so stressed. His boss keeps making him work over time. P = W / t

Energy click on energy for a short video

Energy: Forms and Changes

Nature of Energy Energy is all around you! You can hear energy as sound. You can see energy as light. And you can feel it as wind.

Nature of Energy You use energy when you: hit a softball. lift your book bag. compress a spring.

Living organisms need energy for growth and movement. Nature of Energy Living organisms need energy for growth and movement.

Nature of Energy Energy is involved when: a bird flies. a bomb explodes. rain falls from the sky. electricity flows in a wire.

Energy comes in many forms: mechanical, electrical , magnetic, solar, the ability to do work Energy comes in many forms: mechanical, electrical , magnetic, solar, thermal, chemical, etc... The SI unit of energy is the Joule.

Energy Review how the forms of energy are classified. Use the Forms of Energy handout to begin this discussion.

Energy Kinetic Energy Potential Energy Stored energy and the energy of position Kinetic Energy Motion of waves, electrons, atoms, molecules, and substances Review how the forms of energy are classified. Use the Forms of Energy handout to begin this discussion.

Stored energy and the energy of position Potential Energy Stored energy and the energy of position

Nuclear Energy Chemical Energy Potential Energy Gravitational Energy Energy stored in the bonds of atoms and molecules Nuclear Energy Energy stored in the nucleus of an atom – the energy that holds the nucleus together Potential Energy Stored energy and the energy of position Gravitational Energy Energy of place or position Elastic Energy Energy stored in objects by the application of force.

Motion of waves, electrons, atoms, molecules, and substances Kinetic Energy Motion of waves, electrons, atoms, molecules, and substances

Kinetic Energy Radiant Energy Thermal Energy Sound Energy Electromagnetic energy that travels in transverse waves Thermal Energy Internal energy in substances – vibration or movement of atoms and molecules in substances a.k.a. “heat” Kinetic Energy Motion of waves, electrons, atoms, molecules, and substances Sound Energy Movement of energy through substances in longitudinal waves Electrical Energy Movement of electrons Mechanical Motion Movement of substance from one place to another

GPE = mgh Potential Energy Stored Energy gravitational potential energy GPE = mgh m - mass of object in kg g - acceleration of gravity in m/s2 h - height of object, in m GPE – gravitational potential energy in J

KE = 1/2 mv2 Kinetic Energy energy of motion All moving objects that have mass have kinetic energy. KE = 1/2 mv2 m - mass of the object in kg v - speed of the object in m/s KE - the kinetic energy in J

Different Types of Energy.

Kinetic Energy Anything that moves has kinetic energy.

Gravitational Potential Energy (GPE) Anything above the ground has gravitational potential energy i.e. anything that can fall, like ski jumpers, aeroplanes and climbers.

Nuclear Energy Released only from nuclear reactions The sun and all of the stars. Hydrogen bomb (Fusion) Nuclear power plants

Sound Energy Anything noisy gives off sound energy like vocal chords, speakers and instruments.

Chemical Energy Anything with stored energy which can be released by a chemical reaction has chemical energy, things like food fuels and batteries.

Radiant Energy also called electromagnetic energy All life on Earth depends upon radiant energy from the sun Examples: radio waves, microwaves, X-rays,

Heat/Thermal Energy Anything with a temperature above absolute zero (-273°C) has heat energy. That means everything has some thermal energy.

Light Energy Anything luminous gives off light energy, like the sun, light bulbs , candles and glow worms.

Electrical Energy Electrical energy is very useful, because its easily converted into other forms – wherever there's a current flowing there's electrical energy.

Elastic Energy Anything stretched, has elastic energy – things like rubber bands, springs, knickers, elastic etc

Different types of energy click on link above for a video : thermal light sound elastic gravitational kinetic electrical chemical nuclear Can you think of examples of each type of energy?

Energy transfer Energy can be changed from one form to another. For example: Chemical energy in food is converted to thermal energy and kinetic energy by our bodies. Gravitational energy in a ball is converted to kinetic energy when it falls to the ground. What other energy transfers can you think of?

Energy comes in many forms: mechanical, electrical , magnetic, solar, the ability to do work Energy comes in many forms: mechanical, electrical , magnetic, solar, thermal, chemical, etc... The SI unit of energy is the Joule.

Energy Review how the forms of energy are classified. Use the Forms of Energy handout to begin this discussion.

Energy Kinetic Energy Potential Energy Stored energy and the energy of position Kinetic Energy Motion of waves, electrons, atoms, molecules, and substances Review how the forms of energy are classified. Use the Forms of Energy handout to begin this discussion.

Stored energy and the energy of position Potential Energy Stored energy and the energy of position

Nuclear Energy Chemical Energy Potential Energy Gravitational Energy Energy stored in the bonds of atoms and molecules Nuclear Energy Energy stored in the nucleus of an atom – the energy that holds the nucleus together Potential Energy Stored energy and the energy of position Gravitational Energy Energy of place or position Elastic Energy Energy stored in objects by the application of force.

Motion of waves, electrons, atoms, molecules, and substances Kinetic Energy Motion of waves, electrons, atoms, molecules, and substances

Kinetic Energy Radiant Energy Thermal Energy Sound Energy Electromagnetic energy that travels in transverse waves Thermal Energy Internal energy in substances – vibration or movement of atoms and molecules in substances a.k.a. “heat” Kinetic Energy Motion of waves, electrons, atoms, molecules, and substances Sound Energy Movement of energy through substances in longitudinal waves Electrical Energy Movement of electrons Mechanical Motion Movement of substance from one place to another

What impacts an object’s GPE? Who has more energy? Who has more energy?

GPE = Wh Potential Energy Stored Energy gravitational potential energy W – Weight of object in N h - height of object, in m, GPE – gravitational potential energy in J

Roller Coaster Conversions

The NEED Project

Law of Conservation of Energy “Energy can be neither created nor destroyed. It may only change forms.” energy before the event = energy after the event Examples: A dropped object loses gravitational PE as it gains KE. A block slides across the floor and comes to a stop. A compressed spring shoots a ball into the air.

Law of Conservation of Energy Watch the video and take notes on the law of conservation of energy

Turning on the Light in Your Closet Thermal Sound Radiant Electrical Motion

Describe energy transfer in each device burning match portable torch microphone radio television catapult mobile phone car

Describe energy transfer in each device burning match microphone radio television car chemical to thermal and light sound to electrical electrical to sound and thermal electrical to sound and light and thermal chemical to kinetic and sound and thermal In all these transfers the energy is not lost, it is conserved. Energy cannot be destroyed or created.

Look at the scenes on the slides that follow. Energy poker Look at the scenes on the slides that follow. Make a bid for the number of energy transfers that you can see. The person with the highest bid has to explain where they are. If they fail to find that number they lose. Can you win at energy poker? Let’s look at an example first…

First Example… Energy poker score: 1 Sunlight energy converted into heat to boil the water for tea