题干

关于力对物体做功的叙述,下列说法中正确的是( )

A:举重运动员举着杠铃不动,运动员竖直向上托举的力对杠铃做了功

B:人推汽车但没有推动,人的推力对汽车做了功

C:起重机吊着重物上升,钢绳竖直向上的拉力对重物做了功

D:足球在水平地面上滚动,足球受到的重力对足球做了功

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答案(点此获取答案解析)

C

同类题2

Teens Enjoy Reading
     According to a survey on reading conducted by the U.S. National Education Association (NEA), young Americans say reading is important—more important than computers and science. Over 50% of the twelve to eighteen years old children interviewed said they enjoy reading a lot. Seventy-nine percent find it stimulating and interesting, and 87% think it is relaxing. Most of those surveyed (68%) disagree with the opinion that reading is boring, or old-fashioned.
Teens Read Variety of Material
    Over half the teenagers interviewed said they read more than ten books a year. The results also showed that middle school students read more books than high school students. Most teens (66%) like to read fiction, such as novels and stories. Only 26% were interested in non-fiction, such as biographies and history books. Sixty-four percent of students liked reading ‘stories about people of my own age’ as their favorite topic. Mysteries and detective stories came second on the list at 53%. Just under 50% said they were interested in reading about their own culture and heritage.
Other Interests
    Of the teenagers who took part in the survey, 49% said that libraries are where they get most of their books. However, many complained that their school libraries do not have enough up-to-date, interesting books and magazines. Even though many teenagers in the U.S. enjoy reading, they still have other interests. When asked which activity would be the most difficult to give up for a week, 48% said listening to music. TV would be difficult to give up for 25% of those surveyed.
  ____
    Another survey which is published by www. SmartGirl.com studied the differences between teenage boys' and girls' reading habits. According to the report, more girls than boys read for fun. Many more girls (77%) than boys (6%) read fashion and beauty magazines. More boys (47%)  than girls (7%) read magazines about video games, but an equal number of each like to read adventure stories and newspapers. Girls also read more material about celebrities and social issues such as crime, drugs, or poverty. Boys, on the other hand, read more about sports.

同类题3

阅读短文,回答问题
       骄阳似火。近中午了,可赶集的人还似一股股流水,从四面八方汇集到这弯弯的小路上,形成一条奔流的人河。在人流中,一个小姑娘正推着满满一车杏子摇摇晃晃地走着。路窄,人挤。突然,“唿啦”一声,黄澄澄、水灵灵的甜杏儿在地上滚动起来。呀!无数只脚就要踩到杏子,怎么办?……”
这时,一个洪钟似的喊声压倒吵嚷声:“千万别动!”人群立时静下来,接着,一个拄拐棍的老人弯腰去捡杏子,一个抱孩子的妇女弯腰去捡,一个红领巾弯腰去捡,一个小伙子弯下腰……
     “完了!”姑娘心头一颤,五年前的情景一幕幕浮现在脑海里:一条小路弯弯曲曲,一个小姑娘挑一担苹果在路上走着。拥挤的人流碰翻了筐子,蜂拥而上的人争抢着果子。吃果子的人嘻笑着散开,姑娘掩面哭泣。这姑娘,正是她自己。
    “闺女,别着急。”老人把捡到的杏子放进车里,打断了姑娘的追忆。
    “姑姑,给你。”妇女怀中的孩儿用小手捧着杏儿喊。红领巾踮着脚,努力把捧杏的手伸过来……姑娘不敢相信自己,她擦去泪花,睁大眼睛:不错,都捡回来了,满满的一车杏子。这时,一股清凉的风儿轻轻飘来,姑娘紧锁的眉头舒展开了,脸上泛起了红晕,似一朵乍放的红彤彤的花,可泪花又蒙住了她的眼……噢,是风儿吹到这弯弯的小路上,吹走了千万人心头的炎热,吹开了姑娘脸上的花……