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Unformatted text preview: Gozick, Brandon Homework 14 Due: Oct 31 2006, 7:00 pm Inst: D Weathers 1 This printout should have 10 questions. Multiplechoice questions may continue on the next column or page find all choices before answering. The due time is Central time. 001 (part 1 of 3) 10 points Three particles of mass 6 kg, 1 kg, and 3 kg are connected by rigid rods of negligible mass lying along the y axis and are placed at 5 m, 2 m, and 7 m , respectively as in the figure. The system rotates about the x axis with an angular speed of 1 . 26 rad / s . Contrary to what is observed in the figure, consider the masses to be point particles. 5 m 2 m 7 m 1 . 26 rad / s x 6 kg 1 kg 3 kg Find the moment of inertia about the x axis. Correct answer: 301 kg m 2 . Explanation: Let : m 1 = 6 kg , m 2 = 1 kg , m 3 = 3 kg , y 1 = 5 m , y 2 = 2 m , y 3 = 7 m , and = 1 . 26 rad / s . The total rotational inertia of the system about the x axis is I = X m i r 2 i = 301 kg m 2 , where, r i =  y i  . 002 (part 2 of 3) 10 points Find the total rotational energy of the sys tem. Correct answer: 238 . 934 J. Explanation: Since = 1 . 26 rad / s , the total rotational energy is E = 1 2 I 2 = 1 2 (301 kg m 2 ) (1 . 26 rad / s) 2 = 238 . 934 J . 003 (part 3 of 3) 10 points Find the linear speed of the top particle of mass 6 kg in the figure. Correct answer: 6 . 3 m / s. Explanation: The linear speed of each particles are v i = r i v 1 = r 1 = (5 m) (1 . 26 rad / s) = 6 . 3 m / s . keywords: 004 (part 1 of 1) 10 points Consider the rod plus disc system shown in the figure. m 1 = m , L m 1 = m , R P OP = 3 L /4 O The rod has a length L =1 . 15 m, while the disc has a radius of R = L/ 2 =0 . 575 m. The pivot is at P where the distance between P and the end of the rod is...
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