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Unformatted text preview: Morgan, Mena – Homework 4 – Due: Oct 3 2007, 11:00 pm – Inst: Opyrchal, H 1 This printout should have 9 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 An elevator starts from rest with a constant upward acceleration and moves 1 m in the first 1 . 4 s. A passenger in the elevator is holding a 5 . 5 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: 59 . 5122 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 µ g + 2 h t 2 ¶ = (5 . 5 kg) • 9 . 8 m / s 2 + 2 (1 m) (1 . 4 s) 2 ‚ = 59 . 5122 N . keywords: 002 (part 1 of 1) 10 points Two forces are the only forces acting on a 3 . 1 kg object which moves with an accelera tion of 2 . 7 m / s 2 in the positive y direction. One of the forces acts in the positive x direc tion and has a magnitude of 14 N. What is the magnitude of the other force f 2 ? Correct answer: 16 . 3113 N....
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This note was uploaded on 04/07/2012 for the course PHYSICS 121 taught by Professor James during the Spring '12 term at University of Texas.
 Spring '12
 James
 Physics, Work

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