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Unformatted text preview: Thevalingam, Donald Homework 8 Due: Nov 13 2006, midnight Inst: Eslami 1 This print-out should have 17 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. The due time is Central time. You want to master physics? Solve more problems. You want to solve problems but you cannot? Ask for help after you think about the problem. You do not want to learn physics? Tough luck! 001 (part 1 of 1) 10 points For the ballistic missile aimed to achieve the maximum range of 17500 km, what is the maximum altitude reached in the trajectory? Correct answer: 4375 km. Explanation: For the maximum range R , the launch angle is 45 and the range R is R = v 2 sin(2 ) g = v 2 sin[2 (45 )] g = v 2 g . The height H is given by H = v 2 sin 2 ( ) 2 g = v 2 4 g . So dividing H by R gives H = 1 4 R = 1 4 (17500 km) = 4375 km . keywords: 002 (part 1 of 3) 10 points An object has a mass of 39 kg. The acceleration of gravity is 9 . 8 m / s 2 . What is its weight on the earth? Correct answer: 382 . 2 N. Explanation: g = 9 . 8 m / s 2 and W = m g = 39 kg 9 . 8 m / s 2 = 382 . 2 N 003 (part 2 of 3) 10 points What is its mass on the moon where the force of gravity is 1 6 that of the earth? Correct answer: 39 kg. Explanation: The mass stays the same. 004 (part 3 of 3) 10 points What is the weight of that object on the moon? Correct answer: 63 . 7 N. Explanation: g m = 1 6 g e , so W m = m g m = m g e 6 = (39 kg) 9 . 8 m / s 2 6 = 63 . 7 N keywords: 005 (part 1 of 1) 10 points A ball of mass M is suspended by a thin string (of negligible mass). An upward force F pulls on the string as shown in the figure below. The relation between the tension in the string T and the weight of the ball M g is given in each statement below. M T F Thevalingam, Donald Homework 8 Due: Nov 13 2006, midnight Inst: Eslami 2 While T < M g , the balls acceleration must be constant, with its velocity either up- wards, downwards, or zero. 1. True 2. Cannot be determined. 3. False correct Explanation: In the vertical direction T- M g = m a . Since a = 0 , we have T = M g . The direction of the velocity doesnt matter. keywords: 006 (part 1 of 1) 10 points A man stands in an elevator in the universitys administration building and is accelerating upwards. (During peak hours, this does not happen very often.) Elevator&#13; Cable Choose the correct free body diagram for the man, where F i,j is the force on the object i , from the object j ....
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