國中物理教材內容討論:能量的定義

力學標題:能量的定義. 1:追求真理 國 中 國 中 張貼:2009-04-03 23:43:19: 我想請問一下關於能量它真正的定義是什麼？還有關於能量的單位，牛頓*公尺是焦耳，庫侖*伏特 ... 國立台灣師範大學物理系物理教學示範實驗教室(舊網站)物理問題討論區(黃福坤) 我們也針對科學教學建立開課系統:科學園,讓老師更方便運用網路科技輔助教學，歡迎教師多加利用！中學物理(維基) (學習物理不只是knowHOW更重要的是knowWHY,歡迎參考聞名全球的物理動畫,英文網頁NTNUJAVA以動畫為主) 白話物理 關鍵詞 最近天 物理名詞中英檢索 無法登入或系統功能不正常回報 討論區首頁>>物理課程相關問題(分成國中/高中/大學等區)>>國中物理教材內容討論>>能量的定義 本區註冊且登入者方可留言 想檢測你的物理概念嗎?歡迎到考考你單元(適合國中物理程度)或考考你單元(配合圖片或影片解說)挑戰 力學標題:能量的定義 1:追求真理(國中)張貼:2009-04-0323:43:19: 我想請問一下關於能量它真正的定義是什麼？還有關於能量的單位，牛頓*公尺是焦耳，庫侖*伏特也是焦耳，做功的定義不是施力給物體使其有位移嗎？庫侖與伏特兩單位中含有力與位移的要素嗎？ 2:黃福坤(研究所)張貼:2009-04-0323:58:53:[回應上一篇] 伏特是電位的單位其定義就是單位電荷的電位能 電場則是單位電荷的所受的電交互作用力 3:追求真理(國中)張貼:2009-04-0412:44:24:[回應上一篇] 那我想請問一下教授，能量是否有一個明確的定義，課本好像沒有給他下一個明確的定義 [addsig] 4:黃福坤(研究所)張貼:2009-04-0413:01:51:[回應上一篇] 能量有很多種形式!物體的動能K=(1/2)mV2是一種能量在重力場中有重力位能也是一種形式力施加於一個物體可能改變該物體的動能也可能改變該物體的位能熱能光能等都被發現是各種不同形式的能量而能量之間可以相互轉換!維基百科有能量energy的相關敘述與歷史典故Inphysics,energy(fromtheGreekἐνέργεια-energeia,"activity,operation",fromἐνεργός-energos,"active,working"[1])isascalarphysicalquantitythatdescribestheamountofworkthatcanbeperformedbyaforce.Energyisanattributeofobjectsandsystemsthatissubjecttoaconservationlaw.Severaldifferentformsofenergyexisttoexplainallknownnaturalphenomena.Theseformsinclude(butarenotlimitedto)kinetic,potential,thermal,gravitational,sound,light,elastic,andelectromagneticenergy.Theformsofenergyareoftennamedafterarelatedforce. Anyformofenergycanbetransformedintoanotherform,butthetotalenergyalwaysremainsthesame.Thisprinciple,theconservationofenergy,wasfirstpostulatedintheearly19thcentury,andappliestoanyisolatedsystem.AccordingtoNoether'stheorem,theconservationofenergyisaconsequenceofthefactthatthelawsofphysicsdonotchangeovertime.[2] Althoughthetotalenergyofasystemdoesnotchangewithtime,itsvaluemaydependontheframeofreference. Forexample,aseatedpassengerinamovingairplanehaszerokinetic energyrelativetotheairplane,butnon-zerokineticenergyrelative totheEarth.History Mainarticles:HistoryofenergyandTimelineofthermodynamics,statisticalmechanics,andrandomprocesses ThewordenergyderivesfromGreekἐνέργεια(energeia),whichappearsforthefirsttimeintheworkNicomacheanEthics[3]ofAristotleinthe4thcenturyBC.In1021AD,theArabianphysicist,Alhazen,intheBookofOptics,heldlightraystobestreamsofminuteenergyparticles,statingthat"thesmallestpartsoflight"retain"onlypropertiesthatcanbetreatedbygeometryandverifiedbyexperiment"andthat"theylackallsensiblequalitiesexceptenergy."[4]In1121,Al-Khazini,inTheBookoftheBalanceofWisdom,proposedthatthegravitationalpotentialenergyofabodyvariesdependingonitsdistancefromthecentreoftheEarth.[5] Theconceptofenergyemergedoutoftheideaofvisviva,whichLeibniz definedastheproductofthemassofanobjectanditsvelocity squared;hebelievedthattotalvisvivawasconserved.Toaccountfor slowingduetofriction,Leibnizclaimedthatheatconsistedofthe randommotionoftheconstituentpartsofmatter—aviewsharedbyIsaacNewton,althoughitwouldbemorethanacenturyuntilthiswasgenerallyaccepted.In1807,ThomasYoungwasthefirsttousetheterm"energy"insteadofvisviva,initsmodernsense.[6]Gustave-GaspardCoriolisdescribed"kineticenergy"in1829initsmodernsense,andin1853,WilliamRankinecoinedtheterm"potentialenergy."Itwasarguedforsomeyearswhetherenergywasasubstance(thecaloric)ormerelyaphysicalquantity,suchasmomentum. WilliamThomson(LordKelvin)amalgamatedalloftheselawsintothelawsofthermodynamics,whichaidedintherapiddevelopmentofexplanationsofchemicalprocessesusingtheconceptofenergybyRudolfClausius,JosiahWillardGibbs,andWaltherNernst.ItalsoledtoamathematicalformulationoftheconceptofentropybyClausiusandtotheintroductionoflawsofradiantenergybyJožefStefan. Duringa1961lecture[7]forundergraduatestudentsattheCaliforniaInstituteofTechnology,RichardFeynman,acelebratedphysicsteacherandNobelLaureate,saidthisabouttheconceptofenergy: “ Thereisafact,orifyou wish,alaw,governingnaturalphenomenathatareknowntodate.There isnoknownexceptiontothislaw;itisexact,sofarweknow.Thelaw iscalledconservationofenergy; itstatesthatthereisacertainquantity,whichwecallenergy,that doesnotchangeinmanifoldchangeswhichnatureundergoes.Thatisa mostabstractidea,becauseitisamathematicalprinciple;itsays thatthereisanumericalquantity,whichdoesnotchangewhen somethinghappens.Itisnotadescriptionofamechanism,oranything concrete;itisjustastrangefactthatwecancalculatesomenumber, andwhenwefinishwatchingnaturegothroughhertricksandcalculate thenumberagain,itisthesame. ” —TheFeynmanLecturesonPhysics[7] Since1918ithasbeenknownthatthelawofconservationofenergyisthedirectmathematicalconsequenceofthetranslationalsymmetryofthequantityconjugatetoenergy,namelytime.Thatis,energyisconservedbecausethelawsofphysicsdonotdistinguishbetweendifferentmomentsoftime(seeNoether'stheorem). 5:Learn2Live榮譽點數2點(國中)張貼:2009-04-0417:37:23:[回應上一篇] 有能量就可以做功 [addsig] 6:demo榮譽點數25點(國中)張貼:2009-04-0421:21:35:[回應上一篇] 雖然在學物理的時候常常會講到某能轉化為某能可是我就不明白它們是如何轉變的=='' 例如在斜面上有一個球它從上方滾下來時是由位能轉變為動能  可是是如何轉化的???就沒有人有疑問(難道這是個笨問題嗎???)我一直到想不通喔!! 請各位指指教一下笨笨的我THX^^  [addsig] 7:黃福坤(研究所)張貼:2009-04-0421:43:59:[回應上一篇] 從力的觀點就是沿著斜面的力對球做的功 定義位能是為了更容易計算直接從位能差得知動能的變化!似乎你對於[[位能]]的定義還沒有清楚的理解! 8:demo榮譽點數25點(國中)張貼:2009-04-0619:13:12:[回應上一篇] 我已看過位能的定義了雖然公式把我弄暈~~" 我理解為:把一物體由原點提高到某一高度必雖克服重力所以這時要施加一個力與重力對抗這就是位能(這樣想可以嗎) 由上面得:小球原本在原點位能為零被提升到一定高度必先要施一個力給小球令它能夠克服重力 這是小球的位能一旦這個力不再維持小球在某一高度時則小球不能與重力再對抗所以就會由某一高度 回落為原點這時我們就會說小球的位能轉變為動能(是這樣子嗎??有錯請指正^^) [addsig] 本區註冊且登入者方可留言回首篇留言 黃福坤修改,轉成中文版面並增加功能從2011/06/15起 對本討論區有何疑問請Ruby:onlineid=0:time=1649184365/Apr:0602:04:pagetime=0s