如图所示,重为9N 的物体挂在B 处,O为支点,要想使杠杆保持水平位置平衡,在A 处施加的最小的力是__________N ,方向___________。
3; 竖直向上
常用的氯己定含漱液的浓度是()。
A.0.01%
B.0.02%
C.0.10%
D.0.12%
E.0.15%
When two vessels are in immediate danger of collision,the stand-on vessel must().
A.abandon ship
B.assist in taking whatever action is necessary to avoid collision
C.hold course and speed
D.sound a distress signal