一铰盘有三个等长的柄，长度为<img src="/Image1/9a/9a1ed0804324be5b744784192cc54556.png" />，相互夹角为120°，如图所示。每个柄端作用一垂直于柄大小为P的力，将该力系向BC连线的中点D简化，其结果为（）。 <img src="/Image1/52/522b71c7cd7a3a0a8a16d05abd34a6d8.png" /><br>A:R′＝P，M<img src="/Image1/51/51b47798802e27466bdad55c0bfbe4d5.png" />＝3P<img src="/Image1/9a/9a1ed0804324be5b744784192cc54556.png" /><br>B:R′＝0，M<img src="/Image1/51/51b47798802e27466bdad55c0bfbe4d5.png" />＝3P<img src="/Image1/9a/9a1ed0804324be5b744784192cc54556.png" /><br>C:R′0＝2P，M<img src="/Image1/51/51b47798802e27466bdad55c0bfbe4d5.png" />0＝3P<img src="/Image1/9a/9a1ed0804324be5b744784192cc54556.png" /><br>D:R′＝0，M<img src="/Image1/51/51b47798802e27466bdad55c0bfbe4d5.png" />0＝2P<img src="/Image1/9a/9a1ed0804324be5b744784192cc54556.png" />