bioe119-fall96-final-Keaveny-exam - ME 176 Final Exam, Fall...

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ME 176 Final Exam, Fall 1996 Name: __________________________________________ Page 1 of 10 Wednesday, December 11, 8:00–11:00 AM, 1996. Answer all questions for a maximum of 100 points. Please write all answers in the space provided. If you need additional space, write on the back sides. Indicate your answer as clearly as possible for each question. Write your name at the top of each page as indicated. Read each question very carefully! ____________________________________________________________________________________ 1. (15 points total) Forces and Moments at Joints Flexion-extension injuries occur frequently in vehicle collisions, the so-called “whiplash” injury. In this injury, there is a sudden impact that forces the head into flexion (chin moves towards chest), causing disruption of the posterior ligaments. If the velocity of impact is too high, the ligament can rupture, leading to serious injury of the cervical spine. A. [5 points] Figure 1 shows a simplified diagram of the head, rotating in the counter clockwise direction about the fixed point o , which is the center of the occipital condylar joint at the base of the head. The neck and torso are fixed, simulating a vehicle at full stop after hitting a rigid obstacle with the torso ideally restrained by a seat belt. In this situation, the unrestrained head will continue to move ( i.e. rotate about its base) although the neck and torso are at rest. Convert Figure 1 into a free-body diagram as follows. The (joint) contact force J acts at the joint center through point o and is purely vertical. The vertical (posterior) ligament force F v acts at point p , a horizontal distance d posterior to the joint center; and the horizontal ligament force F h acts through the joint center in the anterior-to-posterior direction. Besides the weight of the head W , there are no other forces acting on this system. The center of mass of the head is at point cg , the velocity of this point is u in the anterior direction; the distance between points o and cg is r ; points o and cg lie on the vertical Y-axis.
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This note was uploaded on 09/16/2009 for the course BIO ENG 119 taught by Professor Keaveny during the Spring '09 term at University of California, Berkeley.

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bioe119-fall96-final-Keaveny-exam - ME 176 Final Exam, Fall...

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