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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 dont mind carrying a heavy load, your backpacks might also power your MP31 player, keep your cell phone running, and maybe even light your way home. The backpacks electricity-creating powers depend on springs used to hang a cloth pack from its metal frame. The frame sits against the wearers 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. 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 arent on the market yet, but if you do get one eventually, just make sure to look both ways before crossing the street! backpack n.背包 watt n. 瓦 night-vision goggle 夜视镜 oscillation n. 摆动 vertical adj. 垂直的 mountaineer n. 登山运动员 注释： 2.Philadelphia：费城[美国宾夕法尼亚州东南部港市] 4.Mass.：Massachusetts 的缩写：马萨诸塞州，美国东北部的一个州。 6.Science：美国的 Science 杂志为国际上著名的自然科学综合类学术期刊，在世界学术界享有盛誉。 Science 杂志创刊于1880年，该杂志具有资讯杂志和学术期刊的双重特点，每周除向世界各地发布有关科学技术和科技政策的重要资讯外，还发表全球科技研究最显著突破的研究论文和报告。 1. Backpacks are convenient because B) they can hold as many things as you want to carry. D) you do not have to carry things with you. | 
