Kinesiology question
No two people walk or run exactly the same. When fitting a person with a lower-limb amputation with a new prosthesis, it is necessarily to choose a prosthesis to provide good performance for the specific individual. This is the job that professional prosthetists do. Consider a person fitted with below-the-knee running-specific prostheses on both legs. The person\'s mass, including prostheses, is 60 kg. Assume that each prosthesis acts like a linear spring with force F_E = k(delta L), where k = 5000 N/m is stiffness and delta t is the deflection of the prosthesis (its decrease in length). What is the person\'s bodyweight? If the person stands with her bodyweight evenly distributed between both prostheses, what is the vertical GRF on each prosthesis? How much will each prosthesis deflect when the person is standing? Does this amount of deflection seem excessive? Assume that the peak ground reaction force (GRF) during running is three times bodyweight. What Is the peak deflection of the prosthesis in contact with the ground? Does this amount of deflection seem excessive? What could the prosthetist do to decrease the peak deflection? In class we compared exoskeletal and endoskeleton lower-limb prostheses. Which type of prosthesis is especially advantageous for a child who is first fitted for a prosthesis at a young age? Is walking with a below-the-knee prosthesis with a dynamic-response foot as metabolically efficient as walking with an intact biological leg?
a) bodyweight = 60Kg * 1 g = 60kg*10m/s^2 = 600N approx of 60 Kg f
b) if person stands evenly, the reaction on each leg is 60/2 kgf = 300 N
c) deflection for each would correcpond to 300 N force, for spring constant of 5000 N/m becomes
300/5000 m or 3/50 m = 6 cm
d) does the deflection seem excessive? maybe if 2.5 inches short is a concern
Homework Sourse
