题干

如图所示,同一物块分别放在水平面和固定斜面上,在两个大小相等的推力F1和F2的作用下运动,F1和F2的方向分别平行于水平面和斜面。若物块在推力的作用下通过的位移相等,则F1、 F2对物块所做的功

A:相等

B:与物块和斜面的粗糙程度有关

C:在水平面上推力所做的功多

D:在斜面一推力所做的功多

上一题 下一题 0.0难度 选择题 更新时间:2016-07-27 07:41:16

答案(点此获取答案解析)

A

同类题2

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。

    Tired of traditional running? Well, maybe it's time to try using your hands instead. That's what Shaun McCarty and other Australians are doing — running on all fours. ____

    McCarthy, who comes from Melbourne, Australia, said he's the one behind the term “crunning.” “It's not crawling, it's not running.” he said. “Crunning is a better workout than running. It puts more of an emphasis(着重)on the body than traditional running does. ____ ”

    McCarthy thinks that he gets much more exhausted after crunning, so he believes it must burn more calories than running.

     ____ Some believe crunning could result in bad shoulder injuries or broken noses.

    But McCarthy is not worried. Many Melbourne residents have been seen running around on all fours. ____ In the Chinese city of Zhengzhou, crawling, a much slower version of crunning, has been a favourite activity for many years. According to some people there, the exercise is believed to date back two thousand years to the Han Dynasty.

     ____ Then McCarthy advises you to buy some good shoes, hand gloves and most important of all, a face mask!

A. Ready to give crunning a try?

B. As it turns out, they are not the only ones.

C. Crunning seems more difficult than traditional running.

D. It really exercises your legs and shoulders at the same time.

E. It's part of the Internet's latest fitness activities: “Crunning.”

F. However, many are not sure if it is the right exercise for humans.

G. He warns, however, that he can't say whether crunning is potentially harmful.