The moment arm of the should abductor muscles is approximately 5 cm from the axis of roation of shoulder joint, and the force vector representing should abductor muscle force is oriented at 150 degrees relative to the positive x-axis. the weight of the upper extremeity of an 80 kg male is about 45 N. if the person is 1.78 m in height, then the center of gravity of the upper-extremity is about .25 m from the shoulder joint.
a) calculate the muscle force needed to hold the arm in static position.
b) calculate the vertical component of the joint reaction force.
c) calculate the horizontal component of the joint reaction force.
d) calculate the orientation of the vector representing joint reaction force.