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第二篇
Electric Backpack
Backpacks are convenient. They can hold your books,your lunch,and a change of clothes,leaving your
hands free to do other things.Someday,if you don't mind carrying a heavy load,your backpacks might also
power your MP3 player,keep your cell phone running,and maybe even light your way home.
Lawrence C.Rome and his colleagues from the University of Pennsylvania in Philadelphia and the
Marine Biological Laboratory in Woods Hole,Mass.,have invented a backpack that makes electricity from
energy produced while its wearer walks.In military actions,search-and-rescue operations,and scientific field
studies,people rely increasingly on cell phones,global positioning system(GPS)receivers,night-vision
goggles,and other battery-powered devices to get around and do their work. The backpack's electricity-generating
feature could dramatically reduce the amount of a wearer's load now devoted to spare batteries,report Rome
and his colleagues in the Sept.Science.
The backpack's electricity-creating powers depend on springs used to hang a cloth pack from its metal
frame.The frame sits against the wearer's back,and the whole pack moves up and down as the person
walks.A gear mechanism converts vertical movements of the pack to rotary motions of an electrical generator,
producing up to 7.4 watts.
Unexpectedly tests showed that wearers of the new backpack alter their gaits in response to the pack's
oscillations,so that they carry loads more comfortably and with less effort than they do ordinary backpacks.
Because of that surprising advantage,Rome plans to commercialize both electric and non-electric versions of
the backpack.
The backpack could be especially useful for soldiers,scientists,mountaineers,and emergency workers
who typically carry heavy backpacks.For the rest of us,power-generating backpacks could make it possible to
walk,play video games,watch TV,and listen to music,all at the same time.Electricity-generating packs
aren't on the market yet,but if you do get one eventually,just make sure to look both ways before crossing
the street!
According to Paragraph 4,what does Rome plan to do?
A:To make the backpack more comfortable for the wearer.
B:To put the backpack on the market.
C:To test the advantage of the backpack.
D:To promote the backpack in a newspaper or on television.

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