(no subject)
Given:
1 and
2 are a linear pair.
Conclusion: m
1 + m
2 = 180 degrees.
Reason: Straight Line Assumption.
Energy expenditure (power) for walking on a level for speed v smaller than 2m/s is approximately given by the expression: P=M+K*v. (At speeds higher than 2m/s the walk is naturally transformed into running. "Race-walking" has higher speeds but involves a very different kind of body motion.) In the expression for power, M represents basal energy spent even when we are standing, which is about 80W.
Why do we need to use energy in order to walk on a horizontal plane?
What is the coefficient K in the above expression?
The kinetic energy of the center of mass is rather significant and should be taken into account but, the kinetic energy is partially used as to modify the potential energy of the center of mass. A very crude approximation would be by considering the work needed to raise center of mass. If the inverted V description is close to reality, then assuming the length of the legs of that V is about 1 m while the size of a step is l=0.5 m we find that the height of the center of mass oscillates between "position" /\ and "position" || by about 3 cm, which for 70 kg person would mean that the potential energy changes by A=20 J. If the walking speed is v, then the number of steps per unit time is v/l, and the power required for such walk is P'=A*v/l. Therefore, A/l=40 N is the coefficient K which we needed to find.
This is, of course, a very crude (under)estimate. Real measurements of energy expenditure show that the coefficient K=160 N (approximately).
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