# Physics

posted by
**john** on
.

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 78.0kg person having arms 69.0cm long and legs 94.0 cm long. The person is running at 12.0km/h, with his arms and legs each swinging through +-30 in 1/2s . Assume that the arms and legs are kept straight.

a)What is the average angular velocity of his arms and legs?

i got 2.09 its correct

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.

Krot=? J

i solved this first ML= .37*78= 28.86kg

MA= .13*78= 10.14 kg

what do i do next im confused

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

Ktotatl=? J

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

i know i have to Krot/ktotal to solve my problem