题干

小磊同学是班里的“大力士”,一天他放学回家,看到公路上有一块大石头,他担心大石头会妨碍车辆正常通行.于是,他决定把石头推到路边,但是他费了很大的力,累得满头大汗,石头却一点儿没动(如图所示).他的同学小颖恰好路过,看到此清景说:“你的行为很值得称赞,但是你对石头并没有做功.”你认为小磊同学对石头做功了吗?为什么?

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答案(点此获取答案解析)

解:小磊对石头没有做功.根据做功的两个必要因素:一是有力作用在物体上,二是物体在力的方向上通过了距离.小磊对石头虽然用了力,但石头没有在力的方向上通过距离.因此,小磊没有对石头做功

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根据短文内容,从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。

Be an inventor

    The biggest secret about inventing is that anybody can do it! Perhaps this sounds crazy, but it's true. Maybe you have the wrong idea about inventing, so read on to discover the truth.

Wrong idea number 1:____

    Well, inventing means creating something “new”, but the idea could come from something that already exists.____ 

Wrong idea number 2: Inventors are born, not made.

    There are a lot of factors that make invention possible. Take Mozart, for example. He was born with a special talent for music.____His father was a music teacher, and Mozart practiced for hours every day, from the time he was in kindergarten.

    ____Very successful creators don't give up when they get something wrong. As one inventor said, “A failure is the right answer to the wrong question!”

    Wrong idea number 3: Inventors are always old people.

____ Here is an example of a young inventor: Louis Braille went blind when he was a child. When he was 15, he invented a system of reading and writing for blind people that is still used in most countries today.

A. Everyday things can give people lots of ideas.

B. An invention has to be something completely new.

C. But other factors were also important for his creativity.

D. As a young man, George Nissen invented the trampoline (蹦床).

E. Don't believe that you can't invent something when you are young.

F. Thomas Edison said that being an inventor was “99% hard work and 1% inspiration”!

G. The Wright brothers, for example, got the idea for building a “flying machine” from watching birds.