Biomedical measurements show that the arms and hands together typically make up

Question

Biomedical measurements show that the arms and hands together typically make up 13.0 of a person's mass, while the legs and feet together account for 37.0 . For a rough (but reasonable) calculation, we can model the arms and legs as thin uniform bars pivoting about the shoulder and hip, respectively. Let us consider a 77.0 person having arms 66.0 long and legs 90.0 long. The person is running at 12.0 , with his arms and legs each swinging through in . Assume that the arms and legs are kept straight.


Part A
What is the average angular velocity of his arms and legs?

Part B
Using the average angular velocity from part A, calculate the amount of rotational kinetic energy in this person's arms and legs as he walks.


Part C
What is the total kinetic energy due to both his forward motion and his rotation?


Part D
What percentage of his kinetic energy is due to the rotation of his legs and arms?

Explanation / Answer

0.5 m v^2 =KE 2. "12 km/h" has two sig figs, so the conversion to m/s should also have two sig figs, i.e. 3.3 m/s, not 3 m/s. And the final answer would have two sig figs, since the mass "72 kg" also has two sig figs.

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