题干

如图所示,放在水平桌面上的物体A通过水平轻绳、轻弹簧和光滑定滑轮与物体B相连接,物体静止时弹簧秤甲和乙的读数分别为5N和2N.若剪断物体A左侧轻绳,则物体A所受的合力和弹簧秤乙的读数分别为(   )

A:5N,零

B:2N,2N

C:零,零

D:零,2N

上一题 下一题 0.0难度 选择题 更新时间:2018-10-12 02:56:30

答案(点此获取答案解析)

D

同类题3

请从以下两道作文题中任选一题作文。

      (一)阅读下面文字,按要求作文。

      缺月变圆,让人明了什么是坚持之后的希望;东归大海的流水,因一往无前,便无可阻挡!回报让乌鸦懂得反哺,感恩会让人想起跪母的羔羊。师长的期待,为青春的生命注入无限的可能;同学的帮助,让少年感受到友谊的力量。小小蚁穴,竟让河堤崩塌;无谓的纷争,多由于缺少谦逊礼让……

生活事事包含哲理,生活处处都是老师。

      请以“生活告诉我”为题,写一篇文章。

      要求:①从自己感受最深、有话想说的角度立意作文;②文体不限,字数不少于600字;③文中不得出现真实的人名、校名、地名。

      (二)阅读下面文字,按要求作文。

      我们有时会站在岔路口,面临选择。

      《散步》中,“儿子”选择有意思的小路,而“我”为了母亲选择平顺的大路。

      《未选择的路》中,“我”选择了一条荒草萋萋、人迹更少的路,虽然一直怀恋着那条未选择的路,但绝不回头。

      《故乡》中,鲁迅写道:“其实地上本没有路,走的人多了,也便成了路。”这句话告诉我们也可以选择一条从未被开辟的道路,自己去创造。

      上述材料引发了你哪些联想与思考?请你写一篇文章,可以讲述经历,也可以阐述观点。

要求:①自拟题目,选好角度,确定立意;②明确文体,但不能写成诗歌;③不少于600字;④不要出现含个人信息的地名、校名、人名等。

同类题4

阅读理解

    The more hours that young children spend in child care, the more likely they are to turn out aggressive and disobedient by the time they are in kindergarten, according to the largest study of child care and development ever conducted. Researchers said this correlation (相关性) held true regardless of whether the children came from rich or poor homes, were looked after by a relative or at a center, and whether they were girls or boys.

    What is uncertain, however, is whether the child care actually causes the problem or whether children likely to turn out aggressive happen to be those who spend more hours in child care. It also remains unclear whether reducing the amount of time in child care will reduce the risk that a child will turn into a mean person. What's more, quality child care is associated with increased skills in intellectual ability such as language and memory, leading some academics to suggest that child care turns out children who are “smart and naughty”.

    The government-sponsored research, which has tracked more than 1,300 children at 10 sites across the country since 1991, is bound to cause the debate over child care again: How should people balance work and family? And how should parents, especially mothers. Resolve the demands that are placed on them to be both breadwinners and supermoms?

    That debate was already on display at a news briefing yesterday, where researchers themselves had different opinions about the data and its implications (含义). “There is a constant relationship between time in care and problem behavior, especially those involving aggression and behavior,” said Jay Belsky of Birkbeck College in London, one of the lead investigators of the study who has previously annoyed women's groups because of his criticisms of child care. “On behalf of fathers or mothers?” interrupted Sarah Friedman, a developmental psychologist at the National Institute of Child Health and Human Development (NICHD) and one of the other lead scientists on the study. “On behalf of parents and families,” responded Belsky.

    “NICHD is not willing to get into policy recommendations.” said Friedman, contradicting her colleague. “There are other possibilities that can be entertained. Yes it is a quick solution—more hours in child care is associated with more problems. The easy solution is to cut the number of hours but that may have implications for the family that may not be beneficial for the development of the children in terms of economics.” In an interview after the briefing, Friedman said that asking parents to work fewer hours and spend more time with their children usually meant a loss of family income, which adversely(不利地) affects children.

    Scientists said that the study was highly reliable. But the researchers said they had no idea whether the behavioral difficulties persisted as the children moved to higher grades.