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Backpacksare convenient.They can hold your books,your lunch,and achangeofclothes,leaving your hands free to do other things.Someday,if youdontmindcarrying a heavy load,your backpacks might also power your MP31player,keepyourcell phone running,and maybe even light your wayhome.

LawrenceC.Rome and his colleagues from the University of Pennsylvania inPhiladelphia2and the Marine Biological Laboratory in WoodsHole3,Mass.4,haveinvented abackpack that makes electricity from energyproduced while its wearerwalks.Inmilitary actions,search-and-rescueoperations,and scientificfieldstudies,people rely increasingly on cellphones,global positioning system(GPS)5 receivers,night-vision goggles,andother battery powered devices to getaroundand do their work.The backpackselectricity- generating featurecoulddramatically reduce the amount of awearer��s load now devoted to sparebatteries,report Rome and his colleaguesinthe Sept.9 Science6.

Thebackpacks electricity-creating powers depend onsprings used to hang aclothpack from its metal frame.The frame sits againstthe wearer��s back,and thewhole pack moves upand down as the person walks.Agear mechanism convertsvertical movements of thepack to rotary motions of anelectricalgenerator,producing up to 7.4 watts.

Unexpectedly,testsshowedthat wearers of the new backpack alter their gaits inresponse to thepacksoscillations,so that they carry loads more comfortably andwith lesseffortthan they do ordinary backpacks.Because of that surprisingadvantage,Romeplans to commercialize both electric and non-electric versionsofthe backpack.

The backpackcould be especially useful orsoldiers,scientists,mountaineers,andemergencyworkers who typically carryheavy backpacks.For the rest ofus,power-generatingbackpacks could make itpossible to walk,play videogames,watch TV,and listen tomusic,all at the sametime.Electricity-generatingpacks arent on the marketyet,but if you do get one eventually,just make sure tolook both ways beforecrossing thestreet!

1.Backpacks are convenient because

�𰸣� yourhands are freed to do other things.

2.What is the most important feature of the backpack invented byLawrenceC.Romeand his colleagues?

�𰸣� Itproduces electricity forelectronic devices while the wearer walks.

3.The word "springs" inParagraph 3 means .

�𰸣� a lengthof metal woundaround,which returns to its original shapeafter

being pushed.

4.Accordingto Paragraph 4,what does Rome plan to do?

A To makethe backpackmore comfortable for the wearer.

�𰸣� To putthe backpack on the market.

5.What isimplied in ��if you do getoneeventually,just make sure to took bothways before crossing thestreet!"?

�𰸣�Enjoyingelectronic devices while walking may invite traffic accidents.


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