I tried to solve this problem twice but i can't get the rightresults.
If a person of mass M simply moved forward with speed V, hiskinetic energy would be 1/2MV2 . However, in addition topossessing a forward motion, various parts of his body (such as thearms and legs) undergo rotation. Therefore, his total kineticenergy is the sum of the energy from his forward motion plus therotational kinetic energy of his arms and legs. The purpose of thisproblem is to see how much this rotational motion contributes tothe person's kinetic energy. Biomedical measurements show that thearms 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 asthin uniform bars pivoting about the shoulder and hip,respectively. In a brisk walk, the arms and legs each move throughan angle of about ±30o (a total of 60o ) fromthe vertical in approximately 1 second. We shall assume that theyare held straight, rather than being bent, which is not quite true.Let us consider a 75.0 person walking at 5.00km/h having arms70.0cm long and legs 90.0cm long.
A)What is the average angular velocity of his arms and legs?
B)Using the average angular velocity from part A, calculate theamount of rotational kinetic energy in this person's arms and legsas he walks.
C)What is the total kinetic energy due to both his forwardmotion and his rotation?
D)What percentage of his kinetic energy is due to the rotationof his legs and arms?
If you want to help, you don't need to solve the whole problem.Just explain how to solve. If you understand or know how to solvethis problem, please help.
I tried to solve this problem twice but i can't get the rightresults.
If a person of mass M simply moved forward with speed V, hiskinetic energy would be 1/2MV2 . However, in addition topossessing a forward motion, various parts of his body (such as thearms and legs) undergo rotation. Therefore, his total kineticenergy is the sum of the energy from his forward motion plus therotational kinetic energy of his arms and legs. The purpose of thisproblem is to see how much this rotational motion contributes tothe person's kinetic energy. Biomedical measurements show that thearms 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 asthin uniform bars pivoting about the shoulder and hip,respectively. In a brisk walk, the arms and legs each move throughan angle of about ±30o (a total of 60o ) fromthe vertical in approximately 1 second. We shall assume that theyare held straight, rather than being bent, which is not quite true.Let us consider a 75.0 person walking at 5.00km/h having arms70.0cm long and legs 90.0cm long.
A)What is the average angular velocity of his arms and legs?
B)Using the average angular velocity from part A, calculate theamount of rotational kinetic energy in this person's arms and legsas he walks.
C)What is the total kinetic energy due to both his forwardmotion and his rotation?
D)What percentage of his kinetic energy is due to the rotationof his legs and arms?
If you want to help, you don't need to solve the whole problem.Just explain how to solve. If you understand or know how to solvethis problem, please help.
