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Unformatted text preview: Anderson, Matthew Homework 4 Due: Oct 3 2007, 11:00 pm Inst: Opyrchal, H 1 This print-out should have 9 questions. Multiple-choice 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 An elevator starts from rest with a constant upward acceleration and moves 1 m in the first 1 . 7 s. A passenger in the elevator is holding a 8 . 9 kg bundle at the end of a vertical cord. The acceleration of gravity is 9 . 8 m / s 2 . What is the tension in the cord as the ele- vator accelerates? Correct answer: 93 . 3792 N. Explanation: T mg a elevator g Let h be the distance traveled and a the acceleration of the elevator. With the initial velocity being zero, we simplify the following expression and solve for acceleration of the elevator: h = v t + 1 2 at 2 = 1 2 at 2 = a = 2 h t 2 . The equation describing the forces acting on the bundle is F net = ma = T- mg T = m ( g + a ) = m g + 2 h t 2 = (8 . 9 kg) 9 . 8 m / s 2 + 2 (1 m) (1 . 7 s) 2 = 93 . 3792 N . keywords: 002 (part 1 of 1) 10 points Two forces are the only forces acting on a 2 . 4 kg object which moves with an accelera- tion of 2 . 1 m / s 2 in the positive y direction. One of the forces acts in the positive x direc- tion and has a magnitude of 5 . 1 N. What is the magnitude of the other force f 2 ? Correct answer: 7 . 17019 N....
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