78. (a) For computing torques, we choose the axis to be at support 2 and consider torques which encourage counterclockwise rotation to be positive. Let m= mass of gymnast and M= mass of beam. Thus, equilibrium of torques leads to 1(1.96m)(0.54m)(3.92m)=0.MgmgF−−Therefore, the upward force at support 1 is F1= 1163 N (quoting more figures than are significant — but with an eye toward using this result in the remaining calculation). In
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