As shown in the figure, a clamping tool hangs a box. The tool includes two identical clamping parts, Abbe and CBDF. The two parts are connected by a smooth shaft at B, and the upper part consists of two parts. As shown in the figure, a clamping tool hangs a box. The tool consists of two clamping parts with the same shape, namely Abbe and CBDF. At B, the two parts are connected by a smooth shaft. Tie two equal-length ropes to the upper part, connect O at both ends and hang them on the crane. The weight of the box is g, and it remains stationary due to the friction between the clamping ends f and h and the box wall. Known AB=BC=FH=a, BD=BE=2a, DF=HE=a/2,? OAB = OCB = 90 degrees. If the quality of the clamp tool is ignored, try to find the pressure of the two clamp ends F and H of the tool on the box.

Solution: t.a+f.a/2 = n.2acos 30,

f=G/2，2Tcos60 =G，

So N=5 times 1.732G/ 12.