solution_pdfj - Patel (sap785) homework #3 shubeita (58645)...

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Unformatted text preview: Patel (sap785) homework #3 shubeita (58645) 1 This print-out should have 16 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. 001 10.0 points A book is at rest on an incline as shown above. A constant force vertically downward is in contact with the book. F B o o k 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. weight force normal friction 2. weight normal friction force 3. weight force normal friction 4. weight force friction normal correct 5. weight friction normal force 6. normal friction weight force 7. normal force friction weight 8. weight friction force normal 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 block from sliding and consequently points up the incline. 002 10.0 points A ball rolls around a circular wall, as shown in the figure below. The wall ends at point X . Patel (sap785) homework #3 shubeita (58645) 2 A B C D E X When the ball gets to X , which path does the ball follow? 1. Path E 2. Path D 3. Path A 4. Path B 5. Path C correct Explanation: As soon as the ball reaches point X the centripetal force is removed, so the ball moves in a straight line (tangent to the circle at oint X). Path C is the correct answer. 003 10.0 points Consider a conical pendulum, where a string with length is attached to a mass m . The angle between the string and the ver- tical is . The orbit is in the horizontal plane with radius r and tangential velocity vectorv . v r g m What is the free body diagram for mass m ? The acceleration of gravity is 9 . 8 m / s 2 . 1. 2. 3. correct 4. 5. Explanation: There are only two forces exerted on the ball, the gravity and the tension on the string. Patel (sap785) homework #3 shubeita (58645) 3 T mg 004 10.0 points A ball is being swung in a horizontal circle at the end of a string at constant speed. Which statement is wrong? 1. The magnitude of vectora depends on the balls speed and the radius of the circle. 2. While the acceleration vectora of the ball is not constant, its magnitude a is constant. 3. The acceleration vector vectora always points directly away from the center of the circle. correct 4. The vectors vectora and vectorv are always precisely perpendicular to one another. 5. While the velocity vectorv of the ball is not constant, its magnitude v is constant. Explanation: From the basic definition vectora = dvectorv dt is directed toward the center of the circle, in such a case....
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This note was uploaded on 04/16/2010 for the course PHY 317k taught by Professor Kopp during the Spring '07 term at University of Texas at Austin.

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solution_pdfj - Patel (sap785) homework #3 shubeita (58645)...

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