搜题请搜索小程序“爱下问搜题”
问题 计算题

如图所示,在长为L的细线下挂一质量为m的小球,用水平恒力F拉小球直到细线偏离竖直方向60°角.求该过程中F所做的功和重力所做的功.

答案

WF=   WG=

拉力和重力都是恒力,可直接应用功的公式计算.

F方向的位移xF=Lsin60°=,

可得F的功WF=F·xF=,

重力方向的位移xG=-L(1-cos60°)=

可得重力的功WG=mgxG=.

问答题

In order to keep good friends together, we must, first of all, show respect to each other; there must not be any, however little, reluctance, interference or dominance involved. Should interest or temperament match, people tend to agree or become friends, or they part company and cease to be friends. You shall never go too far, disregarding manners, no matter what kind of close or intimate friends you are. Otherwise, that state of harmony and balance is sure to be upset and you are no longer friends. Generally, every one of us, as friends, still hopes to have a private room reserved for ourselves. By always having your own ways, you may risk intruding into that forbidden zone, causing conflict or estrangement. Though failing to show respect to friends only seems to be a trifle, it may turn out destructive in the future as if pre-destined. So the best solution for keeping good friends together is stick to showing manners as you see fit in everyday dealings and never meddle: always show respect to each other, and you’ll enjoy lasting friendship.
查看答案
单项选择题

施工过程中，由于甲承包商的分包商施工延误，导致乙承包商不能按进度计划施工，造成费用增加和工期延误，乙承包商应向（）提出索赔意向通知。

A.发包人

B.工程师

C.甲承包商

D.甲承包商的分包商
查看答案