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Unformatted text preview: sanchez (es25396) – Homewor #10  Rotational Motion – guevara – (130101) 1 This printout should have 13 questions. Multiplechoice questions may continue on the next column or page – find all choices before answering. 001 10.0 points A car is moving at 11 m / s along a curve on a horizontal plane with radius of curvature 48 m . The acceleration of gravity is 9 . 8 . What is the required minimum coefficient of static friction between the road and the car’s tires to keep the car from skidding? Correct answer: 0 . 257228. Explanation: The frictional force between the car and the road must supply the centripetal acceler ation necessary to keep the car on the curve. Therefore, we have m v 2 car r = μ F normal = μ m g , so μ = v 2 car g r = (11 m / s) 2 (9 . 8) (48 m) = 0 . 257228 . 002 (part 1 of 2) 10.0 points A hawk flies in a horizontal arc of radius 10 . 3 m at a constant speed of 4 . 8 m / s. Find its centripetal acceleration. Correct answer: 2 . 23689 m / s 2 . Explanation: For constant speed along a circular path, a r = v 2 r = (4 . 8 m / s) 2 10 . 3 m = 2 . 23689 m / s 2 . 003 (part 2 of 2) 10.0 points It continues to fly along the same horizon tal arc but increases its speed at the rate of . 63 m / s 2 . Find the magnitude of acceleration under these new conditions. Correct answer: 2 . 32392 m / s 2 . Explanation: The addition of a tangential acceleration increases the magnitude of acceleration by the vector sum of both accelerations, so a = radicalBig a 2 r + a 2 t = radicalBig (2 . 23689 m / s 2 ) 2 + (0 . 63 m / s 2 ) 2 = 2 . 32392 m / s 2 ....
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 Spring '09
 Guevara
 Force, Correct Answer, Sanchez

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