Runner???s gait. The amount of torque required by an external applied force (other than gravity) to move a leg forward is less than that required to move it backward if the leg is bent as shown in Figure P8.80. The lengths of the vectors r(vector)₁, r(vector)₂, and r(vector)₃indicate the position of the center of mass of the upper leg, lower leg, and foot from the axis of rotation. The ratio of the mass of the upper leg/lower leg/foot is approximately 5/3/1. Find the ratio of the moment of inertia for the leg moving forward to that of the leg moving backward. Approximate the three parts of the leg as point masses.

Figure P8.80

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