An person stands still on one leg

PHYSICS · Multi-part · Fermi University Physics · Fluids & Continuum Physics · Biophysics & Medical Physics · Bioelectricity, the senses and the physics of the body

Life at Thermal Energy, Ch Bones, muscles, blood and body size

Problem

80\,\mathrm{kg}

person stands still on one leg. Take the hip joint reaction force in this stance to be

2.5

times body weight (with

g = 9.8\,\mathrm{m\,s^{-2}}

), carried entirely by the femoral shaft, whose cortical bone has a cross-sectional area of

3.2\,\mathrm{cm^2}

. The measured compressive strength of compact bone is

170\,\mathrm{MPa}

. ((a)) Find the compressive stress in the femoral shaft. ((b)) Express this as a safety factor against failure.

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