# hw7 - ME 577 Human Motion Kinetics Homework#7 Due Friday...

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ME 577 – Human Motion Kinetics Homework #7 Due Friday, April 8 1. Using Hertz contact theory, estimate the impact force when a golf ball hits someone on the top of the head at an initial velocity of 27.5 mph. Due to the composite sandwich structure of the cranial bone, the modulus in radial compression is 2.4 GPa (McElhaney et al., 1970). The mass of a golf ball is 45.30 g and it has a diameter of 4.27 cm. The modulus of the golf ball is approximately 10,000 psi. Recall that V z is the relative speed of the two objects prior to collision and m*, R*, E*, and k are defined by, . Given these definitions, the maximum deformation, δ m , compression time, t c , and the peak force, P m are defined by, . Does the answer make sense? 1 m * = 1 m 1 + 1 m 2 1 R * = 1 R 1 + 1 R 2 1 E * = 1 E 1 + 1 E 2 k = 4 3 R *1/2 E * δ m = 5 m * V z 2 4 k 2/5 t c = m V z P m = k m 3/2

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2. It is possible to compare the forces exerted on the hip in Homo sapiens and Australopithecus
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hw7 - ME 577 Human Motion Kinetics Homework#7 Due Friday...

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