5 11 Exercise Problems Problem 5 1 Consider A Person Holding An Object In His Hand With His Elbow Flexed At The Right An 1 (53.64 KiB) Viewed 56 times
5 11 Exercise Problems Problem 5 1 Consider A Person Holding An Object In His Hand With His Elbow Flexed At The Right An 2 (18.1 KiB) Viewed 56 times
5.11 Exercise Problems Problem 5.1 Consider a person holding an object in his hand with his elbow flexed at the right angle with respect to the upper arm (Fig. 5.4). The forces acting on the forearm and the mechanics model of the system are shown in Fig. 5.5a, b. As for this system assume that the biceps is the major flexor and the line of action of the muscle makes the right angle with the long axis of the forearm. Point O designates the axis of rotation at the elbow joint, A is the point of attachment of the biceps muscle to the radius, point B is the center of gravity of the forearm, and point C is the center of gravity of the object held in the hand. Furthermore, the distances between the axis of rotation of the elbow joint (point O) and points A, B, and C are a = 4.5 cm, b = 16.5 cm, and c = 37 cm. If the total weight of the forearm is W = 83 N, and the magnitude of the muscle force is FM = 780 N: (a) Determine the weight (W) of the object held in the hand. (b) Determine the magnitude of the reaction force (F) at the elbow joint 136 Fundamentals of Biomechanics (c) Determine the magnitude of the muscle (Fmi) and joint reaction (F11) forces when the weight of the object held in the hand is increased by 5 N. Answers: (a) Wo = 57.8 N; (b) F1 = 639.2 N; (c) FM1 = 820 N Fi = 674.2 N
Fig. 5.4 Example 5.1 FM F, a q W w FM F La b B С Ο Α W Wo Fig. 5.5 Forces acting on the lower arm
Join a community of subject matter experts. Register for FREE to view solutions, replies, and use search function. Request answer by replying!