如图所示的几种情况中,不计绳、弹簧测力计、各滑轮的质量,不计一切摩擦,物体质量都为m,且均处于静止状态,有关角度如图所示.弹簧测力计示数FA、FB、FC、FD由大到小的排列顺序是( )
A:FB>FD>FA>FC
B:FD>FC>FB>FA
C:FD>FB>FA>FC
D:FC>FD>FB>FA
温度升高时,温度计内的水银(汞)柱会上升,从微观角度分析,其原因是()
如图,P为⊙O外一点,PA,PB是⊙O的切线,A,B为切点,PA=3,∠P=60°,则图中阴影部分的面积为____ .
– The East Lake is not far from the Yellow Crane Tower, so you can easily visit _________ in a day. – Fantastic! I can't wait for it.