Question

Femur is the main bone in the upper leg. Assume that the minimum cross-sectional area of the femur of a human adult is 6x10-4 m2 . The weight of the human is 70 kg. The ultimate compression strength for bone is 17 x 107 N.m-2. The Young’s modulus for bone in compression is 0.9 x 1010 N.m-2.

1. What is the compression load at which fracture occurs? Comment on the size of this force and compare it with the weight of the human.
2. Assuming that stress-strain relationship for the bone is linear until fracture, find the strain at which the fracture occurs. Calculate the reduction in length of the bone when the fracture occurs.
3. The experimental value of the strain is slightly larger. Explain what the reason could be for this discrepancy. Draw a strain – stress diagram for this situation.

Answer 1