4-Lucy_L_Avenue-4 - 1 PHYS 1L03, W inter 2011, McMaster...

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Unformatted text preview: 1 PHYS 1L03, W inter 2011, McMaster University LUCY Human Evolution and Physics Bipedalism,Quadrupedalism Concepts: Center of mass Torque Force Equilibrium Chapters: 4, 5 Pages: 95-101, 122-141 PHYS 1L03, W inter 2011, McMaster University Who is Lucy ? PHYS 1L03, W inter 2011, McMaster University Lucy A partial hominid skeleton, discovered at Hadar, Ethiopia, Africa in 1974. This individual is assigned to Australopithecus afarensis. Lucy is a female adult, 3.5 feet tall. PHYS 1L03, W inter 2011, McMaster University Fi g u r e 0 4 .1 2 c PHYS 1L03, W inter 2011, McMaster University Australopithecus An early hominid genus, from Africa Characterized by bipedal locomotion Earliest known bipedal ancestors of humans (prior to humans) PHYS 1L03, W inter 2011, McMaster University Lucy A 40% complete skeleton of Lucy indicates that she was bipedal . Lucys entire skeleton was reconstructed from the remains that were discovered. 2 PHYS 1L03, W inter 2011, McMaster University Lucy Why do we think Lucy was bipedal (walking upright)? What requirement is needed for effective and efficient bipedal posture and locomotion? Comparison between Chimpanzee ( quadruped, knuckle walking ) and Human ( biped, upright walking ) PHYS 1L03, W inter 2011, McMaster University Quadrupedalism vs. Bipedalism Knuckle Walking Human bipedal PHYS 1L03, W inter 2011, McMaster University Quadrupedalism vs. Bipedalism In this comparison, the following questions are considered: Does walking upright need considerable change to the shape of the pelvis bones? Does walking upright create a change in the position of the center of mass. Does walking upright need change to the function of gluteal (abductor) muscles? PHYS 1L03, W inter 2011, McMaster University Quadrupedalism vs. Bipedalism To answer these questions, we need to know Physics of: What is Center of Mass? What is weight line? What is Force? What does force do? Already we studied them (previous chapter). What is Torque? What does torque do? What is mechanical equilibrium? PHYS 1L03, W inter 2011, McMaster University Center of Mass Center of mass (CM) of a system is the point at which all the mass of the system may be considered to be concentrated. The system may be either a group of objects (particles) or an extended object like our body. Center of Mass The system may be an extended object like our body. The translational motion of the center of mass of the system is the same as if the mass of the system is concentrated at that point. PHYS 1L03, W inter 2011, McMaster University 3 PHYS 1L03, W inter 2011, McMaster University Center of Mass For an extended object, like our body, different parts move with different speed....
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4-Lucy_L_Avenue-4 - 1 PHYS 1L03, W inter 2011, McMaster...

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