Spiral fracture of bone: Spiral fracture of bone occurs due to twisting of the limb, and is a very common skiing accident. The fracture plane is helical, and is very difficult to heal. Mechanically, it occurs due to an applied torsion load on the bone. Recall that a state of pure shear occurs within the material when torsion is applied on a cylinder, and the bone can be idealized as a cylinder. Let a femur bone be subjected to a torque of T 50 N-m. Assume body weight of the person to be W- 80 Kgs, while each leg is subjected to half of that weight. Given radius of the bone r 10 mm. Compute the principal stresses and shear stresses, as well as orientation of planes on which these stresses are realized.