Question

Anna is standing on her left foot. Her right leg is Abducted approximately 20o at the hip. Her left arm is Abducted 60o at the glenohumeral joint.

     Brian is standing on his right foot. His left leg is flexed 90o at the knee. Each arm is slightly Abducted at the glenohumeral joint (15o) and flexed (90o) at the elbow.

      Catherine is standing on her right foot. Her left leg is Abducted 60o at the hip. Each arm is Abducted 100o at the glenohumeral joint.

     Mike is standing on both feet. His left arm is flexed 180o at the glenohumeral joint. His right arm is slightly Adducted past anatomical position so it crosses in front of his body.

If each dancer has the same angular momentum about the longitudinal axis, then which dancer has the greatest velocity and which dancer has the lowest velocity?

Answer 1

Angular momentum L = I

givne that

L_A = L_B = L_C = L_M , angular momentum is same for all the dancers.

=> I_AA= I_BB= I_CC = I_MM

Nothing is stated about the MI ofach dancer when standing normal , we assume they are same

Anna has pulled her leg and foot farther from the Body center compared to Brain, hence

I_A > I_B , part of the mass is away from axis of rotation and hence the MI is greater

Catherine has pulled part of the body mass fartehr than Anna , hence

I_C > I_A

Mike has his body mass closets to his body center, hence

I_M is the least

I_C > I_A > I_B > I_M

hence _M (Mike) is the larget and _C (Catherine) is the least.