Question

Short answer questions. Please show your work with detailed steps and circle your final answers. (30 points) 1. A model is used to divide the right lower extremities into three segments: the right thigh, right shank, and right foot. Table I below shows the coordinates of the proximal and distal joints to define these segments. Table II shows relative segment center of mass locations and relative segment mass as a percent of total body mass. The total body mass is 50 kg. (12 points). Keep 3 decimal places. Table I Marker Right Toe Right Ankle Right Knee Right Hip 0.5 0.3 0.45 0.1 Y (m) 0.3 0.3 0.65 0.8 Table II Segment Relative center of mass Relative mass as a percent location 45% fromn ankle to toe Foot Shank Thigh of total body mass 190 3% 10% 40% from knee to ankle 40% from, hip to knee a. Use the marker positions and relative center of mass locations to calculate the center of mass locations of the right thigh, the right shank, and the right foot in both X and Y directions. b. Use the center of mass locations you have calculated in question a and the relative mass to find the overall center of mass of the entire right lower extremity in both X and Y directions. c. Will the overall center of mass location you calculate in b change if the total body mass is 100 kg instead of 50kg?

Answer 1

center of mass calculation i) The right thigh h X bar = x of hip + x of knee/2 X bar = 0.1 + 0.45/2 X bar = 0.275 Y bar = y of hip + y of knee/2 = 0.8 + 0.65/2 Y bar = 0.725 Hence center of mass location of right thigh = (0.275, 0.715) ii) For shank X bar = 0.45 + 0./2 = 0.375, Y bar = 0.65 + 0.3/2 Y bar = 0.475 (0.375, 0.475) \r\n iii) For the right foot X bar = 0.3 + 0.5/2 X bar = 0.4, Y bar = 0.3 + 0.3/2 Y bar = 0.3 (0.4, 0.3) b) From table Mass of foot = 1 % of body mass = M/100 (where M is whole body mass) Mass of shank = 3 % of body mass = 3 M/100 Mass of thigh = 10 % of body mass = 10 M/100 mass of entire right lower extremely =