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Unformatted text preview: ME 104: Engineering Mechanics II Spring Semester 2011 Department of Mechanical Engineering University of California at Berkeley Professor Oliver M. O’Reilly Homework No. 12 Additional Help and Intermediate Results Notes: These is the homework help file for Homework 12. It discusses the assignments and gives helpful pointers on how to set up and solve the problems. The 5 problems featured in this homework involve using the balance laws: F = m ¯ a , and Either M = ˙ H or M O = ˙ H O . (1) In all but one of the problems, ω = ˙ θ E z and H = I zz ˙ θ E z . Consequently, you can easily use H O = H + ¯ x × m ¯ v to work out (for all but the one problem) H O = I Ozz ˙ θ E z . Alternatively, given I zz you can use the parallel–axis theorem to work out I Ozz . For all of these problems, you should use The Four Steps . The algebra can be involved so I recommend that you insert numbers at the very end. 1. Problem 6/39 (Non SIProblem) (20 Points) First, you need to pick an origin O . Next, put a corotational basis on the bar and use it to calculate ¯ x , ¯ v , H O of the bar. The easiest choice here is to have e x pointing along the bar so that ¯ x = L e x , where L = 0 . 25 feet In step II, you will need to compute the total moment M O acting on the bar. Don’t forget the vertical gravita tional force − mg E z and the moment M c ....
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This note was uploaded on 02/22/2012 for the course ME 104 taught by Professor Oreilly during the Spring '08 term at Berkeley.
 Spring '08
 Oreilly
 Mechanical Engineering

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