题干
- When is Women's Day?
- It's _____ March 8th.
A：in
B：of
C：on
D：at
答案(点此获取答案解析）
C
- When is Women's Day?
- It's _____ March 8th.
A：in
B：of
C：on
D：at
50 N和70 N，它们与水平地面之间的动摩擦因数均为0.2，与A、B相连接的轻弹簧被压缩了5 cm，系统置于水平地
面上静止不动。已知弹簧的劲度系数为100 N/m。用F
=7N的水平力作用在木块A上，如图所示，力F作用后( )