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举一反三
【单选题】一绞盘有三个等长的柄,长度为 L ,相互夹角为 120 0 如图所示。每个柄端作用一垂直于柄的力,且 P 1 =P 2 =P 3 =P 。将该力系向 BC 连线的中点简化,结果为( ) 。
A.
R=P, M=3PL
B.
R=2P, M=3PL
C.
R=0 , M=3PL
D.
R=0 , M=2PL
【单选题】YJ17卷烟机蜘蛛手机构抽吸槽回转至最左位置时，其（）。
A.
水平速度为零，垂直速度最大
B.
水平速度最大，垂直速度为零
C.
水平速度为零，垂直速度为零
D.
水平速度最大，垂直速度最大
【单选题】In one way of thinking, failure is a part of life. In another way, failure may be a way towards success. The ―spider story‖ is often told. Robert Bruce, leader of the Scots in the 13th century, was hi...
A.
The think about the cause of your failure
B.
to check out whether your goals are right for you
C.
to consider failure as a part or life
D.
to bear in mind that you will never fail in your life
E.
to tell him that he should cheer up
F.
To warn him that failure is terrible