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Unformatted text preview: Overton, Mays Homework 10 Due: Feb 14 2005, 4:00 am Inst: Turner 1 This printout should have 12 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 A(n) 864 N crate is being pushed across a level floor by a force of 396 N at an angle of 25 above the horizontal. The coefficient of kinetic friction between the crate and the floor is 0.20. The acceleration of gravity is 9 . 81 m / s 2 . 864 N k = 0 . 20 3 9 6 N 25 What is the acceleration of the box? Correct answer: 1 . 73295 m / s 2 . Explanation: Let : W = mg = 864 N , F applied = 396 N , = 25 , k = 0 . 20 , and g = 9 . 81 m / s 2 m F a p p l i e d mg N k N Basic Concepts: F applied,x = F applied cos F applied,y = F applied sin F y,net = F n + F applied,yW = 0 F k = k F n F x,net = ma x = F applied,x F k Solution: F applied,x = (396 N)cos25 = 358 . 898 N F applied,y = (396 N)sin25 = 167 . 357 N The normal force is F n = W + F applied,y = 864 N + 167 . 357 N = 1031 . 36 N . The mass of the crate is m = W g = 864 N 9 . 81 m / s 2 = 88 . 0734 kg . From the horizontal motion, ma x = F applied,x k F n a x = F applied,x k F n m = 358 . 898 N (0 . 2)(1031 . 36 N) 88 . 0734 kg = 1 . 73295 m / s 2 across the floor. 002 (part 1 of 1) 10 points A 3.70 kg block is pushed along the ceiling with a constant applied force of 90.0 N that acts at an angle of 62.0 with the horizontal. The block accelerates to the right at 6.80 m/s 2 . The acceleration of gravity is 9 . 81 m / s 2 . 3 . 7 kg 9 N 6 2 6 . 8 m / s 2 What is the coefficient of kinetic friction between the block and the ceiling? Correct answer: 0 . 395949 . Explanation: Overton, Mays Homework 10 Due: Feb 14 2005, 4:00 am Inst: Turner 2 Basic Concepts: F applied,x = F applied cos F applied,y = F applied sin F y,net = F applied,y mg F n = 0 F x,net = ma x = F applied,x F k F k = k F n m F a Given: m = 3 . 70 kg = 62 . F applied = 90 N a x = 6 . 80 m g = 9 . 81 m / s 2 Solution: F applied,x = (90 N)cos62 = 42 . 2524 N F applied,y = (90 N)sin62 = 79 . 4653 N The normal force is F n = F applied,y mg = 79 . 4653 N (3 . 7 kg)(9 . 81 m / s 2 ) = 43 . 1683 N From the horizontal motion, ma x = F applied,x k F n k = F applied,x ma x F n = 42 . 2524 N (3 . 7 kg)(6 . 8 m / s 2 ) 43 . 1683 N = 0 . 395949 003 (part 1 of 3) 10 points The suspended 2 . 6 kg mass on the right is moving up, the 1 . 4 kg mass slides down the ramp, and the suspended 7...
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This note was uploaded on 03/22/2008 for the course PHY 303K taught by Professor Turner during the Spring '08 term at University of Texas at Austin.
 Spring '08
 Turner
 Physics, Work

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