一个截面是直角三角形的木块放在水平地面上,在斜面上放一个光滑

一个截面是直角三角形的木块放在水平地面上,在斜面上放一个光滑球,球的一侧靠在竖直墙上,木块处于静止,如图10所示。若在光滑球的最高点再施加一个竖直向下的力F,木块仍处于静止,则木块对地面的压力N和摩擦力f的变化情况是            (    )

A.N增大,f增大

B.N增大,f不变

C.N不变,f增大

D.N不变,f不变

 

答案

A

解析:略

 

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