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Unformatted text preview: Muraj, Hamza Homework 23 Due: Mar 27 2006, 4:00 am Inst: Florin 1 This printout should have 8 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 1) 10 points Consider the diatomic molecule oxygen, O 2 , which is rotating in the xy plane about the z axis passing through its center, perpendicular to its length. The mass of each oxygen atom is 2 . 66 10 26 kg, and at room temperature, the average separation distance between the two oxygen atoms is 2 . 76 10 10 m(the atoms are treated as point masses). If the angular speed of the molecule about the z axis is 5 . 18 10 12 rad / s, what is its rotational kinetic energy? Correct answer: 1 . 35925 10 20 J. Explanation: Since the distance of each atom form the z axis is d/ 2 (where d = 2 . 76 10 10 m is the separation distance between the two oxygen atoms), the moment of inertial about the z axis is I = 2 X n =1 m n r 2 n = m d 2 2 + m d 2 2 = 1 2 md 2 , where m = 2 . 66 10 26 kg is the mass of an oxygen atom. Using the formula for the rotational kinetic energy, we obtain K R = 1 2 I 2 = 1 4 md 2 2 = 1 . 35925 10 20 J . 002 (part 1 of 3) 10 points Three particles of mass 8 kg, 3 kg, and 2 kg are connected by rigid rods of negligible mass lying along the y axis and are placed at 8 m, 3 m, and 4 m , respectively as in the figure. The system rotates about the x axis with an angular speed of 2 . 87 rad / s . Contrary to what is observed in the figure, consider the masses to be point particles. 8 m 3 m 4 m 2 . 87 rad / s x 8 kg 3 kg 2 kg Find the moment of inertia about the x axis. Correct answer: 571 kg m 2 . Explanation: Let : m 1 = 8 kg , m 2 = 3 kg , m 3 = 2 kg , y 1 = 8 m , y 2 = 3 m , y 3 = 4 m , and = 2 . 87 rad / s . The total rotational inertia of the system about the x axis is I = X m i r 2 i = 571 kg m 2 , where, r i =  y i  . 003 (part 2 of 3) 10 points Find the total rotational energy of the sys tem. Correct answer: 2351 . 63 J. Explanation: Muraj, Hamza Homework 23 Due: Mar 27 2006, 4:00 am Inst: Florin 2 Since = 2 . 87 rad / s , the total rotational energy is E = 1 2 I 2 = 1 2 (571 kg m 2 ) (2 . 87 rad / s) 2 = 2351 . 63 J ....
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This note was uploaded on 04/12/2010 for the course PHY 58195 taught by Professor Turner during the Spring '09 term at University of Texas at Austin.
 Spring '09
 Turner

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