【单选题】Youth Council of Arlington The Youth Council of Arlington is an association dedicated to improving the lives of young people through education in leadership skills, personal growth, and economic indep...
A.
To raise money for school trips
B.
To help local youth lead productive lives
C.
To renovate the community center
D.
To provide training in accounting practices
【单选题】关于超声波液位计下列说法不正确的是()。
B.
封闭管道用超声波流量计按测量原理主要有传播时间法和多普勒效应法
D.
超声波流量计可以将其传感器安装在管道外部,不和介质接触,不需要开孔,只要将换能器安装在管道表面即可
【简答题】如图4-16,劲度系数为k的弹簧一端固定在墙上,另一端连接一质量为m的物体,放在光滑水平面上,弹簧原来没有伸长.现将一质量为M的物体轻轻地挂在绳端的钩A上,试求物体M的最大速度(设绳子不可伸长、质量可以忽略,滑轮与绳间无摩擦).
【多选题】下列关于多普勒效应的说法,正确的是( )。
A.
医院检查身体的“B超”仪运用了多普勒效应原理。
B.
不仅机械波,电磁波和光波也会发生多普勒效应。
C.
由地球上接受到遥远天体发出的光波发生“红移”现象(各条谱线的波长均变长),可以判断遥远天体正靠近地球。
D.
静止的观察者听到某个单一频率声源发出的声音频率越来越高,说明声源正在远离观察者。
【单选题】The WT O’s top level decision-making body is the Ministerial Conference . Below this is the General Council . At t he next level, the Goods Council, Services Council and Intellectual Property (TRIPS) ...
A.
the Trade Policy Review Body
B.
the Dispute Settlement Body
D.
the Committee on Martet Access