*75.   The drawing shows an outstretched arm (0.61 m in length) that is parallel to the floor. The arm is pulling downward against the ring attached to the pulley system, in order to hold the 98-N weight stationary. To pull the arm downward, the latissimus dorsi muscle applies the force  in the drawing, at a point that is 0.069 m from the shoulder joint and oriented at an angle of 29°. The arm has a weight of 47 N and a center of gravity (cg) that is located 0.28 m from the shoulder joint. Find the magnitude of.

 

w0451

Free body diagram is shown above.  Take the torques about the shoulder point and three forces cannot produce torques, the x and y components of the shoulder force and the x component of the muscle force.  So the sum of the torques is

 

 

 

 

 

 

 

 

 

 

 

 

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This page last updated on January 11, 2020