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Unformatted text preview: arellano (aa39398) Homework 8 weathers (17101) 1 This print-out should have 12 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. 001 (part 1 of 2) 10.0 points An amusement park ride consists of a rotating circular platform 9 . 07 m in diameter from which 10 kg seats are suspended at the end of 1 . 61 m massless chains. When the system rotates, the chains make an angle of 16 . 9 with the vertical. The acceleration of gravity is 9 . 8 m / s 2 . l d What is the speed of each seat? Correct answer: 3 . 85958 m / s. Explanation: In the vertical direction we have T cos = mg , where T is the tension in the chain. In the horizontal direction we have T sin = mv 2 r . Since r = sin + d 2 = (1 . 61 m) sin16 . 9 + 9 . 07 m 2 = 5 . 00303 m , we have v = radicalbig g r tan = radicalBig (9 . 8 m / s 2 ) (5 . 00303 m) tan16 . 9 = 3 . 85958 m / s . 002 (part 2 of 2) 10.0 points If a child of mass 47 . 9 kg sits in a seat, what is the tension in the chain (for the same angle)? Correct answer: 593 . 031 N. Explanation: M = 47 . 9 kg From the first part we have T cos = ( m + M ) g T = ( m + M ) g cos = (10 kg + 47 . 9 kg) (9 . 8 m / s 2 ) cos 16 . 9 = 593 . 031 N . 003 10.0 points A curve of radius 50 . 8 m is banked so that a car traveling with uniform speed 51 km / hr can round the curve without relying on fric- tion to keep it from slipping to its left or right. The acceleration of gravity is 9 . 8 m / s 2 . 2 . 1 M g What is ? Correct answer: 21 . 9559 . Explanation: Let : m = 2100 kg , v = 51 km / hr , r = 50 . 8 m , and . Basic Concepts: Consider the free body diagram for the car. The forces acting on arellano (aa39398) Homework 8 weathers (17101) 2 the car are the normal force, the force due to gravity, and possibly friction. N N N cos mg N sin x y To keep an object moving in a circle re- quires a force directed toward the center of the circle; the magnitude of the force is F c = ma c = m v 2 r ....
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This note was uploaded on 10/31/2010 for the course PHYSICS 1710 taught by Professor Weathers during the Fall '10 term at North Texas.
- Fall '10