Twisting Forces on Bones: Which Will Fracture First?

The shorter bone will fracture first.

This is because the longer bone has a higher moment of inertia, which means that it can resist twisting forces more effectively. The moment of inertia of a bone is proportional to its length to the fourth power, so even a small difference in length can make a significant difference in its resistance to twisting.

In addition, the longer bone will be subjected to a smaller twisting force per unit area than the shorter bone. This is because the twisting force is distributed over a larger area in the longer bone. As a result, the stress on the material of the bone will be lower in the longer bone, and it will be less likely to fracture.

Therefore, if two bones of equal radius are subjected to twisting forces, the shorter bone will fracture first.