题干
.
--- When will you be through with your work, Jones?
--- ______ My boss usually finds something for me to do at the last minute.
--- When will you be through with your work, Jones?
--- ______ My boss usually finds something for me to do at the last minute.
A：Who knows.
B：Would you help me?
C：I beg your pardon?
D：Anything the matter?
答案(点此获取答案解析）
A
点的三个力平衡，设其中一个力大小为
，沿
轴负方向，另一个大小未知的力
与
轴正方向夹角为
，那么关于第三个力
，下列判断正确的是( )
（ ）