DW=F·c d M F·cr (+) M F=、i+E,j+Ek dr= dki+ dvi+dzk (F,dx+F,dy+F dz) OW=F·cr=F,wt =  =  2 1 M M W d W d F r  F r r i j k F i j k d dx dy dz Fx Fy Fz = + + = + +  = + + 2 1 ( ) 1 2 M M W Fx dx Fy dy Fz dz  =  =  =  2 1 M M W dt W d dt F v  F r F v