题干

如图所示,是一种自行车的打气筒的截面示意图,其中有一处地方结构没有画全,请根据打气的原理和过程,在图上补全结构,并用文字简要说明这种打气筒跟普通气筒不同的打气原理.

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答案(点此获取答案解析)

解:当打气筒打气时,筒内气压高于轮胎内气压时,筒内的空气会通过小筒 进入轮胎内,若当轮胎内气压大于筒内气压时,为了防止轮胎漏气,需在小筒右侧进气管处应装有活门,空气只能进入小筒,不能从小筒回到右侧大筒,答案见下图;同时这种打气筒加有小筒的目的是:打气时能在小筒中储存压缩气体,比较均匀地向车胎里打气.

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    Typing with one hand when the other one is occupied can be a real pain, so imagine having to type with just one foot. It's got to be a nightmare, but 21-year-old Hu Huiyuan from China's Anhui Province is using her only functional foot to write not just a few sentences, but an entire fiction novel!

    Born prematurely(过早地), Hu was diagnosed with cerebral palsy(脑瘫) when she was only 10 months old. This left her permanently paralyzed—the only parts of her body she can move are her head and left foot. As she grew older, she learned how to perform everyday tasks using her foot.

    Despite not having received formal education, Hu is surprisingly well-spoken. Over the years, with the help of her mother, she taught herself to read and write. “I'm not a genius, but I'm very focused,” she said, modestly. “When I watched TV in my childhood, I often learned words on the screen.”

    “When I was teaching her how to speak, I had to repeat every single word a thousand times before she got it, ”Hu's mother said. “But once she mastered the word. I felt satisfied.”

    With time going by, Hu's language got so proficient that she set out to write a story about the pursuit of dreams and love. She's doing this by typing out every single word on her computer using only one foot.

    In spite of all these setbacks, Hu is able to type 20 to 30 words a minute. She has already written six chapters—that's 60,000 words—and says she only has two more chapters to go before the novel is complete.