正方体的重心原高H0=L/2
现高H=根号(2(L/2)^2)=L根号(1/2)
重心升高H-H0=L/2-L根号(1/2)=L(根号2)/2-L/2
=L((根号2)-1)/2
=L(1.414-1)/2
=L0.414/2
=0.207L