Date

Chapter fiveMain Points

Date

5-1

Energy:ORIGIN mid 16th cent. (denoting force or vigor of expression): from French énergie, or via late Latin from Greek energeia, from en- ‘in, within’ + ergon ‘work.’3 Physics the property of matter and radiation that is manifest as a capacity to perform work

✤Energy is the ability to _____________ __________.

✤Mr. Martin sez: It’s also the ability to __________ __________.

Cause Change

do work

What does that mean?

✤Energy can cause a change in a substance’s _________, ________, ________, _________, or _________.

✤Other examples?

locationtemperature velocity

positionacceleration

Joules

✤ Last chapter, we defined joules as:

✤ 1. the SI unit of work.

✤ 2. the amount of ENERGY require to raise a one newton weight by one meter.

Joules: are also...

✤Well, if energy is the ability to do work...

✤And if joules measure an amount...

✤Joules are the amount of energy used to cause a change (p. 125)

Elastic Potential Energy

✤ The energy stored in an object as a result of deformation of an object

✤ stretched; compressed; bending, twisting, shearing

✤ springs; bow & arrow; bouncy ball; catapult, rubber band

✤ http://www.physics247.com/physics-help/elastic-potential.shtml

✤ http://hyperphysics.phy-astr.gsu.edu/Hbase/pespr.html

✤ http://en.wikipedia.org/wiki/Elastic_energy

Gravitational Potential Energy

✤ the energy an object has when it is in an elevated position

✤ anything that can fall or drop

✤ books on a desk; swing on a swingset; drop of water on a faucet; baseball in the air; hot air balloon

Chemical Potential Energy

✤Energy stored due to the arrangement of molecules

✤Fuel, food

Electrostatic Potential Energy

✤Energy stored in electrical charges

Potential Energy Therefore...

✤Energy stored in an object

✤bent out of shape, or elevated;

✤fuel, or electric charge

Kinetic Energy✤ The opposite of Potential Energy.

✤ Potential is stored in an object

✤ Kinetic, therefore, is not stored--it is in motion

✤ Kinetic Energy: The energy an object has due to its mass and motion.

✤ “Anything in motion has kinetic energy”.

What does this feller have to do with p. 127?

✤ Hint: His most famous formula says that the mass of a body is a measure of its energy content.

http://blog.syracuse.com/shelflife/2008/03/einstein2.jpghttp://en.wikipedia.org/wiki/File:Relativity3_Walk_of_Ideas_Berlin.JPG

e= energy; m=massc=constant speed of light

✤ e= mc2 means that if you know the mass of an object, you can measure the amount of energy it has.

✤ Einstein: energy = mass x speed of light2

✤ p. 127: kinetic energy = mass x speed2

_____________2

http://en.wikipedia.org/wiki/Kinetic_energy

✤ There are several different equations that may be used to calculate the kinetic energy of an object. In many cases they give almost the same answer to well within measurable accuracy. Where they differ, the choice of which to use is determined by the velocity of the body or its size. Thus, if the object is moving at a velocity much smaller than the speed of light, the Newtonian (classical) mechanics will be sufficiently accurate; but if the speed is comparable to the speed of light, relativity starts to make significant differences to the result and should be used.

Section Two Vocab:

✤ First Law of Thermodynamics:

✤ Energy can NOT be created

✤ Energy can NOT be destroyed

✤ Energy CAN be changed from one form to another

Section Two Vocab:

✤ Second Law of Thermodynamics:

✤ Whenever energy is converted, waste is produced.

✤ Results: No machine is 100% efficient

✤ Waste Heat, friction, waste sound occur

✤ Energy input never quite matches energy output

Section Two Vocab:

✤ Perpetual Motion: a machine which, once started, would continue operating forever with no loss of motion, no waste heat, no friction, and no additional energy input

✤ Impossible due to Second Law of Thermodynamics

Refrigerators vs. Air Conditioners

✤ p. 132--heating coils on the back of the refrigerator

✤ my Air Conditioner

✤ my returning the Air Conditioner story

✤ http://www.buy.com/retail/product.asp?sku=206724967&listingid=30320586

http://en.wikipedia.org/wiki/File:Air_conditioning_unit-en.svg

http://www.flickr.com/photos/prettywarstl/1084809231/sizes/l/

http://www.flickr.com/photos/kellbell62683/2071404697/sizes/l/

5-3

Section Three Vocab:

✤Heat: The Total Kinetic Energy of the Moving Atoms and Molecules of a Substance (139)

Section Three Vocab:

✤Temperature:

The Average Kinetic Energy of the Moving Atoms and Molecules of a Substance(140)

Section Three Vocab:

✤Thermal Expansion: an increase in the size or volume of a substance due to an increase in the motion of its molecules and atoms

Section Three Vocab:

✤Conduction(142): Transfer of Heat energy from one substance to another by DIRECT CONTACT

✤Conductors(143): Materials and substances that (readily) allow the transfer of heat

Section Three Vocab:

✤ Insulators(143): Materials and substances that limit the amount of heat that passes through them

✤ Convection(144): the transfer of heat in liquids and gases as groups of molecules move in currents

✤ Radiation(145): the transfer of heat energy by electromagnetic waves

Three types of heating

✤Conduction: A stovetop

✤Convection: A mirage, a room heater, an aquarium

✤Radiation: Sunlight

Main Points of Chapter Five:

Main point #1

✤First Law of Thermodynamics: Energy often changes form

Main Point #2

✤ Second Law of Thermodynamics:

✤ When Energy Changes Form, waste is created in the forms of light, heat (friction), sound

✤ No machines work perfectly

✤ My air conditioner;

Main Point #3

✤ Potential Energy is found in fuel, food, gravity, elasticity

✤ Anything in motion has kinetic energy

✤ When you are swinging on a swingset, energy changes from kinetic, to potential, to kinetic, to potential; the more kinetic, the less potential

Main Point #4

✤ The difference between heat and temperature

✤ Heat is total; Temperature is average kinetic energy of the moving atoms and molecules of a substance

Main Point 5:Three types of Heating

✤ Conduction: DIRECT CONTACT--frying pan

✤ Convection: CURRENTS of heat in a fluid--requires a medium--something to move through

✤ Radiation: heat in ELECTROMAGNETIC WAVES--can go through empty space

Thanks for Watching!