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Unformatted text preview: reddy (ar38357) – Newton’s Laws and Circular Motion – clancy – (SCI411-2) 1 This print-out should have 12 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 10.0 points A car rounds a curve while maintaining a constant speed. Is there a net force on the car as it rounds the curve? 1. No – its speed is constant. 2. Yes. correct 3. It depends on the sharpness of the curve and speed of the car. Explanation: Acceleration is a change in the speed and/or direction of an object. Thus, because its direction has changed, the car has accelerated and a force must have been exerted on it. 002 10.0 points A ball rolls around a circular wall, as shown in the figure below. The wall ends at point X . A B C D E X When the ball gets to X , which path does the ball follow? 1. Path B 2. Path C correct 3. Path A 4. Path D 5. Path E 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 When you are in the front passenger seat of a car turning to the left, you may find yourself pressed against the right-side door. What concept(s) explain(s) why you press against the door and why the door presses on you? 1. centrifugal force and Newton’s first law 2. centrifugal force and Newton’s second law 3. just a centrifugal force 4. Newton’s first and third laws correct Explanation: Newton’s first and third laws provide a straight-forward explanation. You tend to move in a straight line (Newton’s first law) but are intercepted by the door. You press against the door because the door is pressing against you (Newton’s third law). The push by the door provides the centripetal force that keeps you moving in a curved path. Without the door’s push, you wouldn’t turn with the car - you’d move along a straight line and be thrown out . Centrifugal forces are fictitious. 004 10.0 points A motorcyclist is able to ride on the vertical wall of a bowl-shaped track as shown. His weight is counteracted by the friction of the wall on the tires (vertical arrow)....
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This note was uploaded on 11/21/2010 for the course PHYS 12231 taught by Professor Sontar during the Fall '10 term at Ill. Chicago.

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solution_pdf13 - reddy(ar38357 – Newton’s Laws and...

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