10. Consider a person doing lateral arm raises as illustrated in the figure to the right....

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10. Consider a person doing lateral arm raises as illustrated in the figure to the right. Such arm raises are a good workout for the deltoid muscles, which we will consider as the primary movers during the upward motion. The weight of the arm is 50 N, the weight being lifted is 50 N, the inertia of the arm about the shoulder joint is 0.15 kg-m, the length of the arm is 75 cm, and the center-of-mass of the arm is located 25 cm from the shoulder. a. Draw the free body diagram and kinetic diagram for the arm when it is at a horizontal position. You may assume that the deltoid attaches to the arm at a distance of 5 cm from the shoulder at an angle of 15 with respect to the long axis of the arm. b. As the arm passes through the horizontal position the force of the deltoids is 1540 N, the angular velocity is 10 rad/s upwards, and the angular acceleration is 200 rad/s downwards. What is the horizontal joint reaction force? C. Discuss how the joint reaction forces in part (b) compare to the horizontal reaction force if the arm was being held statically at this same horizontal position. Hint: you will first need to solve for the force in the deltoid to hold the arm in the horizontal position. [Answer: (b) 1360 N if you ignore the weight being lift, 977 N if you include it] 10. Consider a person doing lateral arm raises as illustrated in the figure to the right. Such arm raises are a good workout for the deltoid muscles, which we will consider as the primary movers during the upward motion. The weight of the arm is 50 N, the weight being lifted is 50 N, the inertia of the arm about the shoulder joint is 0.15 kg-m, the length of the arm is 75 cm, and the center-of-mass of the arm is located 25 cm from the shoulder. a. Draw the free body diagram and kinetic diagram for the arm when it is at a horizontal position. You may assume that the deltoid attaches to the arm at a distance of 5 cm from the shoulder at an angle of 15 with respect to the long axis of the arm. b. As the arm passes through the horizontal position the force of the deltoids is 1540 N, the angular velocity is 10 rad/s upwards, and the angular acceleration is 200 rad/s downwards. What is the horizontal joint reaction force? C. Discuss how the joint reaction forces in part (b) compare to the horizontal reaction force if the arm was being held statically at this same horizontal position. Hint: you will first need to solve for the force in the deltoid to hold the arm in the horizontal position. [Answer: (b) 1360 N if you ignore the weight being lift, 977 N if you include it]