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BIO Bone Fractures. The maximum energy that a bone can
Chapter 9, Problem 10E(choose chapter or problem)
BIO Bone Fractures. The maximum energy that a bone can absorb without breaking depends on characteristics such as its cross-sectional area and elasticity. For healthy human leg bones of approximately 6.0 cm2 cross-sectional area, this energy has been experimentally measured to be about 200 J. (a) From approximately what maximum height could a 60-kg person jump and land rigidly upright on both feet without breaking his legs? (b) You are probably surprised at how small the answer to part (a) is. People obviously jump from much greater heights without breaking their legs. How can that be? What else absorbs the energy when they jump from greater heights? (?Hint:? How did the person in part (a) land? How do people normally land when they jump from greater heights?) (c) Why might older people be much more prone than younger ones to bone fractures from simple falls (such as a fall in the shower)?
Questions & Answers
QUESTION:
BIO Bone Fractures. The maximum energy that a bone can absorb without breaking depends on characteristics such as its cross-sectional area and elasticity. For healthy human leg bones of approximately 6.0 cm2 cross-sectional area, this energy has been experimentally measured to be about 200 J. (a) From approximately what maximum height could a 60-kg person jump and land rigidly upright on both feet without breaking his legs? (b) You are probably surprised at how small the answer to part (a) is. People obviously jump from much greater heights without breaking their legs. How can that be? What else absorbs the energy when they jump from greater heights? (?Hint:? How did the person in part (a) land? How do people normally land when they jump from greater heights?) (c) Why might older people be much more prone than younger ones to bone fractures from simple falls (such as a fall in the shower)?
ANSWER:Solution 10E Step 1: Data given Mass m = 60 kg Area of cross section A = 6.0 cm 2 Energy W = 200 J W = KE = PE = mgh 200J × 2 = 400 J 400 J is the energy used for both legs 400 J = mgh 400 J = 60 kg × 9.8 m/s × h 400 J h = 60 kg ×9.8 m/s h = 0.680 m From this we can note that the person has to jump from 0.680 m to stand upright without breaking any bone