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Biomedical measurements show that the arms and hands together typically make up 13.0 % of a persons 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 76.0 kg person having arms 68.0 cm long and legs 93.0 cm long. The person is running at 12.0 km/h , with his arms and legs each swinging through 30° in 1/2 s. Assume that the arms and legs are kept straight.
a) What is the average angular velocity of his arms and legs?
b) Calculate the amount of rotational kinetic energy in this persons arms and legs as he walks.
c) What is the total kinetic energy due to both his forward motion and his rotation?
d) What percentage of his kinetic energy is due to the rotation of his legs and arms?
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Our tutors have indicated that to solve this problem you will need to apply the Intro to Rotational Kinetic Energy concept. You can view video lessons to learn Intro to Rotational Kinetic Energy. Or if you need more Intro to Rotational Kinetic Energy practice, you can also practice Intro to Rotational Kinetic Energy practice problems.
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Based on our data, we think this problem is relevant for Professor Petty's class at HAWAII.