Energy, Work, and Simple Machines

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law of conservation of energy of conservation law

is the conversion of one form of energy to of one form of energy is the conversion Read the two statements below and decide below statements Read the two

The . Even though energy can change forms, the can be transformed. an object. pull push or to to force Energy cannot be created or destroyed, but it or destroyed, cannot be created Energy Work describes how much energy it takes for a it takes for much energy describes how Work 4. 3. . For example, suppose a zoo uses a heat lamp to . For example, suppose a zoo uses As you read in Lesson 1, different types of electric energy As you read in Lesson 1, different it moves from one object Energy also is transferred when Suppose you turn on a lamp switch. The radiant energy Before Statement After What do you think? do you What column an A in the Before with them. Place or disagree agree whether you read you’ve After disagree. or a D if you with the statement agree if you mind. changed your have you see if to the statements this lesson, reread to another. When energy is transferred, the form of energy When energy is transferred, the form of energy to another. does not have to change. For example, the thermal energy in the heat lamp is transferred to the air and then to the zebra. coming from the bulb had many other forms before it shined in your eyes. The radiant energy was electric energy in the and it was chemical energy in the fuel at the wiring, lamp’s electric energy plant. plants supply the energy you use in your home and school. plants supply the energy you use transformation Energy another energy in the wiring warm a newborn zebra. The electric energy. the heat lamp is transformed into thermal of Energy Conservation Energy Energy Transformations Energy Energy, Work, and Simple Simple and Work, Energy, Machines Work and Transformations Energy created or destroyed created total amount of energy in the universe does not change. It just changes form. energy can be transformed from one form to another, but it cannot be but it cannot one form to another, from be transformed can energy

OCABULARY d read, you As What is the law What is the law d n V i . 8 0 4 9 8 to change form or 8 Key Concept Check Concept Key _ 2 L _ E and Simple Machines Work, Energy, Reading Essentials How are energy and work and work energy are How related? What is the law of What is the law conservation of energy? can energy In ways what be transformed? R CADEMIC _ transform (verb) structure 2 of conservation of energy? 46

1. Define teacher. A use sticky notes to mark use sticky to notes do not that you information Read the text understand. If time. a second carefully a write help, still need you ask your list of questions to Sticky Notes • Key Concepts Concepts Key • • 1 0 _ 8 0 0 _ 3 5 3 CC353_008_012_RE_L2_889408.indd 8 CC353_008_012_RE_L2_889408.indd 9 3 5 3 _ 0 0 8 _ 0 1 2 _ R E

_ Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. L 2 _ 8 8 9 4 0 transformed toelectricenergy. wind, geothermal,andhydroelectricenergy—are energy plants.Atthesefacilities,formsofenergy—solar, other formsofenergyalsocanbetransformedatelectric you useinyourhomeandschool.AsreadLesson1, chemical energyistransformedtotheelectricthat ago, transforms.Atelectricenergypowerplants,that stored inthemoleculesofplantsthatlivedmillionsyears edn setas nry ok n ipeMcie Energy, Work, andSimpleMachines Reading Essentials Energy and Work Energy PowerElectric Plants Plants andtheBody Roller Coasters direction oftheforce whilethe force ontheobject acts transfer ofenergy thatoccurs whenaforce makes move anobject inthe But sciencedoesnotdefinestudyingaswork. turned theplantsintofossilfuels. pressure fromthesedimentsthatcoveredplantremains died, theywereburiedundersediment.Aftermuchtime, chemical energyintheirm These ancientplantsstoredradiantenergyfromtheSunas photosynthesis justliketheplantsthatarealivetodaydo. movement, temperaturecontrol,andotherlifeprocesses. transforms thechemicalenergytoyourbodyneedsfor up thebroccoli.Thisreleaseschemicalenergy. Your body breaks apartthechemicalbondsinmoleculesthatmake plant’s molecules.Whenyoueatthebroccoli,yourbody energy. Thechemicalenergyisstoredinthebondsof it transformsradiantenergyfromtheSunintochemical next hill. to gravitationalpotentialenergyasyourcarmovesupthe lot ofkineticenergy. Thiskinetic your gravitationalpotentialenergyissmall, transformed tokineticenergy. Atthebottomofhill, faster andfaster. Thegravitationalpotentialenergyis increases. Next,yourcarracesdownthehill.You move between youandEarthincreases. your cartothetopofabighill.Atthispoint,distance that occuronarollercoaster?Mostcoastersfirstpull 8 . i n d d When a plant, such as broccoli, carries on photosynthesis, When aplant,suchasbroccoli,carriesonphotosynthesis, Have youeverthoughtabouttheenergytransformations When youstudyforatest,itmightfeellikelotofwork. Whenfossilfuelsburn,thechemicalenergy, whichwas Plants thatlivedmillionsofyearsagocarriedon

9 olecular bonds.Aftertheplants energy is Your potential energyalso transformed b but youh . Work

is the ave a ack energy thegreatest? gravitational potential a roller coaster rideis between work andenergy. words, therelationship summarize, inyour own half-booktoCreate avertical 2. Apply make electric energy.make electric transformations thatoccur to 3. Identify Reading Check

Key Concept Check

energy?

How is

work to At whatpointin three energy 44/3/10 1:12:45PM 47 / 3 / 1 0

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0 1 / 3 / 44/3/10 1:13:38 PM Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. Upward force weight Drums’ the object moves during The drummer is no longer doing work on work drummer is no longer doing The not the drums because the drums are in the direction of the applied force. moving Work Work also depends on the distance Work Recall that forces are pushes or pulls. When you lift an are pushes Recall that forces the boy is standing still On the right in the figure above, How much work do you do when you lift your backpack object must move in the direction of the force. Work is done is done Work of the force. object must move in the direction is moving the object. only while the force off the ground? The amount of work depends on the force of 20 N, you do If you lift a backpack with a force you apply. of 40 N. less work than if you lift with a force object, you transfer energy from your body to the object. As object, you transfer energy from figure above, the drums move the boy lifts the drums in the As the drums move higher above and have kinetic energy. The surface, they gain gravitational potential energy. Earth’s boy has done work on the drums. Because he is not moving the with his drums lifted in place. an object, an do work on drums, he is not doing work. To Doing Work less work than if you lift it 2 m. Suppose you toss a backpack When you release it, it continues moving upward. in the air. Even though the backpack is still moving when you let go, no work is being done. This is because you are no longer applying to the backpack while it is in the air. a force the time the force is applied. If you lift a backpack 1 m, you do is applied. If you lift the time the force What 0 If you do work do work If you 1

d d n i . 8 0 4 9 8 he lifts them. The drums’ kinetic energy and and kinetic energy drums’ The he lifts them. increase. energy potential gravitational The drummer does work on the drums as on the drums drummer does work The 8 Key Concept Check Concept Key _ 2 L Visual Check Visual _ E and Simple Machines Work, Energy, Reading Essentials R Upward force _ Drums’ weight Drums’ 2 energy transformations transformations energy lifted? as the drums are occur 48

5. Describe 4. Recognize 4. Recognize on an object, will its how change? energy 1 0 _ 8 0 0 _ 3 5 3 CC353_008_012_RE_L2_889408.indd 10 CC353_008_012_RE_L2_889408.indd 11 3 5 3 _ 0 0 8 _ 0 1 2 _ R E

_ Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. L 2 _ 8 8 9 4 0 it isnoteasilyusedtodousefulwork. heat. Scientistssometimescallthisheat higher temperaturetoaregionofloweriscalled surroundings. Thermalenergymovingfromaregionof thermal energy. Thisthermalenergyistransferredtothe energytransfer,and every someenergyistransformedinto energytransformation transfers ittothewheelaxle.Inevery For example,acar’s enginetransformsenergyfromfueland in thetirescausesrubbertogiveoffaburntodor. energy. quickly, Ifracecarsaremovingvery thermalenergy the kineticenergyoftirestotransformintothermal the motion. other. Thedirectionoffrictionisintheopposite friction isaforce betweentwosurfacesincontactwitheach contact, andtheymovepasteachotherquickly. Recallthat of racecarsaremaderubber. Thetiresandtheroadarein newton-meter (N·m).Aisajoule(J). is inmeters(m).Theproductofnewtonsand work (injoules) Work Equation on it. moves inthedirectionofforce whiletheforce isacting applied totheobject. edn setas nry ok n ipeMcie Energy, Work, andSimpleMachines Reading Essentials Energy andHeat Calculating Work 8 . i n d d As aracecarmoves,energyistransformedandtransferred. Frictionbetweenacar’s tiresandtheroadcausessomeof The force intheequationisnewtons(N),anddistance Have youeverheardthephrase The equationforworkisshownbelow.

1 1 W

= =

force (innewtons) Fd Distance isthedistanceobject burning rubber burning × distance(inmeters) waste energy Force istheforce ? Thetires because done is60J. Answer: The amountofwork she doonthechair? How muchwork doesheor 0.75 mwithaforce of20N. The studentpullsthechair chair inorder to sitdown. A studentpullsouthisorher 6. Solve for Work d. c. b. a. the bag? work doesthestudentdoon a force of50N.How much 1.2 mabove thefloor, using floor to hisorhershoulder abagfrom the A studentlifts Math Skills Use thisformula:

W and multiply: F Substitute thevaluesfor distance: force: W work: work: This iswhatyou know: You needto find: and

= = = 60N·m (50N)

Fd d W into theformula d F

= = × = 50N 1.2m (1.2m) 60J 44/3/10 1:14:28PM 49 / 3 / 1 0

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onnect the transfer of energy that occurs when a force makes an an makes a force when occurs that of energy the transfer C object move in the direction of the force while the force acts while the force in the direction of the force object move on the object Log on to ConnectED.mcgraw-hill.com ConnectED.mcgraw-hill.com on to Log find this to textbook your and access resources. lesson’s work: work: a principle that says that that says a principle that the conversion of one form of of one form of the conversion 2 1

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8 _ 2 L energy to another to energy cannot be created or destroyed cannot be created energy can be transformed from one form to another, but it another, one form to from can be transformed energy _ E Write a question about something you marked with a sticky note. Then answer the a question about something you Write your teacher. question from what you learned by rereading the lesson or asking The figure below depicts a hill in the middle of a roller coaster ride. On each line, The figure below depicts a hill that is occurring at that point in the ride. identify the energy transformation Review the terms and their definitions in the Mini Glossary. Write a sentence that Write Mini Glossary. and their definitions in the Review the terms during photosynthesis. transformation that occurs describes an energy agree with the statement or a D if you disagree. disagree. or a D if you the statement with agree mind? change your Did you Reread the statements at the beginning of the at the beginning the statements Reread with an A if you column in the After lesson. Fill and Simple Machines Work, Energy, Reading Essentials R What do you think _ 2 50 3. 2. 1. Mini Glossary energy transformation: of conservation of energy: law 1 0 _ 8 0 0 _ 3 5 3 CC353_008_012_RE_L2_889408.indd 12