The femur of a human leg (mass 10 kg, length 0.9 m) is in traction (see figure). The center of gravity for the leg is one third of the way from the pelvis to the bottom of the foot. Two masses are hung via pulleys to provide an upward support: the mass m1 at the pelvis and the mass m2 at the foot. A third mass of 8 kg is hung to provide tension along the leg. The body itself provides tension but no shear.
What is the mass m1?