Of the 10 electroweak particles Table 181 which ones travel at or near lightspeed To travel at or near lightspeed the mass needs to be zero or extremely close to zero The photon with zero mass will certainly travel at lightspeed The neutrinos with a ID: 56366
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canexistontheirownasasingleparticle,butquarksmustbeconned ,appearingonlywithotherquarks.2Problems2.)\Aproton-antiprotonpair,atrest,annihilateandcreatetwophotons.Usingtheinfor-mationintheprecedingproblem,andthefactthataprotonis1,800timesmoremassivethananelectron,ndthefrequencyofeachphoton."Theinformationfromtheprecedingproblemstatesthatthefrequencyofphotonsemittedwhenanelectron-positronpairannihilateis1020Hz.Theprocessforthistohappenise�+e+!2 ,where standsforaphoton.Wewilluseenergyconservation,settingtheinitialenergyequaltothenalenergy.Theinitialenergycomesjustfromrestmass:Ei=2mec2,wheremeisthemassofanelectron/positron(theyhavethesamemass),andthefactorof2comesfromthefactthattheelectronandpositionhavethesamemass.Thenalenergyistheenergyofthetwophotons:Ef=2hfe,wherefe=1020Hzisthefrequencywearetoldfromproblem1.).EnergyconservationsaysEi=Ef!2mec2=2hfe.Simplifyingthisexpressionbydividingoutthecommonfactorof2:mec2=hfe.Howdowegureoutthefrequencyforaprotonandantiproton?Theonlythingdif-ferentisthemass:themassoftheproton/antiprotonis1800timesthemassoftheelec-tron/position.Thus,wecanincreasethemassbyafactorof1800,andseewhathappenstothefrequency:(1800me)c2=h(1800fe).Thus,thefrequencyincreasesby1800aswell!Thenewfrequencyis 18001020Hz=1:81023Hz .4.)\Makingestimates.Alargeelectricpowerplantgenerates1000MWofelectricity.Iftheenergycamefrommatter-antimatterannihilation,aboutwhattotalmassofmatterandofantimatterwouldberequiredeachyear,assumingthattheelectricityisgeneratedatanenergyeciencyof50%?"Themainideaweneedisthis:(Energyneededfor1year)=(energyfrommatter-antimatterannihilation).Let'sworkontheleft-handsiderst:togettheenergyneededfor1year,wewillmultiplythepowerby1year,inseconds(thisworksbecausepowerisenergydividedbytime-weneed1yearinsecondsbecauseaWatt=1Joule/1sec,andmultiplyingbysecondscancelsthoseunits,leavinguswithJoules).Energyneededfor1year=(Power)(1yearinsec)=1000MW(3:1107sec)=1000106W(3:1107sec)=3:11016J:(1)Nowletsworkontheright-handside:theenergyfrommatter-antimatterannihilationcomesmainlyfromthe(unknownamountof)restmassofthematterandantimatter(seeprob(2)above):2mc2.However,theplantoperatesat50%eciency,soweonlygethalfof2