1.A man holds an object by extending his arm horizontally as shown in the diagram below. A corresponding simplified mechanical model is also depicted. His deltoids (shoulder muscles) were found to be exerting a force of 1000 N. The line of action of his deltoids is located at 15° away from the bone in his arm and acts at a distance of 0.12 m from the shoulder joint. His arm weighs 3 kg and its centre of mass is located at a distance of 0.25 m from the shoulder joint.
a) Assuming that the centre of gravity (CG) of the object is located at 0.6 m away from the shoulder joint and taking moments about the shoulder joint,
i.what is the magnitude and direction of the moment generated by the pull of the deltoids?
ii.what is the magnitude and direction of the moment generated by the weight of the arm?
iii.hence, what is the weight of the object?
b) What is the magnitude of the reaction force acting on the shoulder joint?