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Unformatted text preview: schroeder (cs39963) Quiz 6: Circular Motion and Gravitation balasubramanya (1401310) 1 This printout should have 38 questions. Multiplechoice questions may continue on the next column or page find all choices before answering. 001 10.0 points A fighter plane flying at constant speed 450 m / s and constant altitude 5500 m makes a turn of curvature radius 5500 m. On the ground, the planes pilot weighs (65 kg) (9 . 8 m / s 2 ) = 637 N. What is his/her apparent weight during the planes turn? Correct answer: 2476 . 51 N. Explanation: The planes altitude is not important per se , but the fact that it is constant tells us that the plane moves in a horizontal plane and its normal acceleration a N = v 2 R = 36 . 8182 m / s 2 has a horizontal direction. Furthermore, con stant speed implies zero tangential accelera tion, hence vectora = vectora N . The apparent weight of the pilot combines his true weight mvectorg and the inertial force mvectora due to planes acceleration, vector W app = m ( vectorg vectora ) . In magnitude,  vectorg vectora  = radicalbig g 2 + a 2 = 38 . 1001 m / s 2 because vectora is horizontal while vectorg is vertical. Consequently, the pilots apparent weight is vector W app = (38 . 1001 m / s 2 ) (65 kg) = 2476 . 51 N , which is quite heavier than his/her true weight of 637 N. 002 10.0 points As viewed by a bystander, a rider in a barrel of fun at a carnival finds herself stuck with her back to the wall. Which diagram correctly shows the forces acting on her? 1. 2. correct 3. None of the other choices 4. 5. 6. Explanation: The normal force of the wall on the rider provides the centripetal acceleration neces sary to keep her going around in a circle. The downward force of gravity is equal and oppo site to the upward frictional force on her. schroeder (cs39963) Quiz 6: Circular Motion and Gravitation balasubramanya (1401310) 2 Note: Since this problem states that it is viewed by a bystander, we assume that the freebody diagrams are in an inertial frame. 003 10.0 points A motorcyclist is able to ride on the vertical wall of a bowlshaped track as shown. His weight is counteracted by the friction of the wall on the tires (vertical arrow). A drawing of the vectors for the forces that acts on the cyclist is shown below. The vec tors are drawn from the center of mass of the motorcyclist. N f mg r Which force(s) increase(s) or decrease(s) if he rides faster? 1. Only the normal force decreases. 2. The frictional and normal forces increase. correct 3. Only the frictional force decreases. 4. The frictional and normal forces de crease. 5. Only the frictional force increases. 6. Only the normal force increases....
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 Fall '08
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 Physics, Circular Motion, Force, Friction, General Relativity, Correct Answer, Schroeder

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