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# OldHW10 - hiarker(srh959 oldhomework 10 Turner(58220 This...

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hiarker (srh959) – oldhomework 10 – Turner – (58220) 1 This print-out should have 11 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 10.0 points The system is in equilibrium and the pulleys are frictionless and massless. 9 kg 6 kg 7 kg 1 2 3 T Find the force T . The acceleration of grav- ity is 9 . 8 m / s 2 . Correct answer: 401 . 8 N. Explanation: Let : m 1 = 9 kg , m 2 = 6 kg , and m 3 = 7 kg . m 1 m 2 m 3 1 2 3 T T 4 T 3 T 3 T 3 T 2 T 1 T 1 The mass m 1 defines the tension T 1 : T 1 = m 1 g . At pulley 3, T 1 acts down on either side of the pulley and T 2 acts up, so T 2 = 2 T 1 = 2 m 1 g. At the mass m 2 , T 3 acts up, and m 2 g and T 2 act down, so T 3 = m 2 g + T 2 = m 2 g + 2 m 1 g . At pulley 2, T 3 acts up on either side of the pulley and T 4 acts down, so T 4 = 2 T 3 = 2 m 2 g + 4 m 1 g . At the mass m 3 , T 4 = T + m 3 g T = T 4 m 3 g = (2 m 2 + 4 m 1 m 3 ) g = [2 (6 kg) + 4 (9 kg) (7 kg)] (9 . 8 m / s 2 ) = 401 . 8 N . keywords: 002 (part 1 of 2) 10.0 points A book is at rest on an incline as shown below. A hand, in contact with the top of the book, produces a constant force F hand vertically downward. F hand Book The following figures show several attempts at drawing free-body diagrams for the book. Which figure has the correct directions for each force? The magnitudes of the forces are not necessarily drawn to scale. 1. normal friction weight force

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hiarker (srh959) – oldhomework 10 – Turner – (58220) 2 2. weight normal friction force 3. weight friction normal force 4. weight force normal friction 5. normal force friction weight 6. weight force friction normal correct 7. weight friction force normal 8. weight force normal friction Explanation: The normal force points perpendicular to the surface of the inclined plane. The weight force points down. The F hand also points down. The friction force keeps the book from sliding and consequently points up the incline.
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OldHW10 - hiarker(srh959 oldhomework 10 Turner(58220 This...

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