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Unformatted text preview: schneiter (tcs639) HW03 Ross (89152) 1 This print-out should have 10 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. 001 (part 1 of 2) 10.0 points A motorist is traveling at 14 m / s when he sees a deer in the road 47 m ahead. If the maximum negative acceleration of the vehicle is- 7 m / s 2 , what is the maximum reaction time t of the motorist that will allow him to avoid hitting the deer? Correct answer: 2 . 35714 s. Explanation: Let : v = 14 m / s , v = 0 , and a =- 7 m / s 2 . Basic Concept: v = x t v 2 = v 2 + 2 a x . Solution: v 2 = v 2 + 2 ax stop x stop =- v 2 2 a = 14 m . x- x stop = v t. This yields t = x- x stop v = 2 . 35714 s . 002 (part 2 of 2) 10.0 points If his reaction time is 2 . 54604 s, how fast will he be traveling when he reaches the deer? Correct answer: 6 . 08475 m / s. Explanation: Let: t = 2 . 54604 s Solution: x slow = x- v t . We again use the relation v 2 = v 2 + 2 a x slow , which gives v = radicalBig v 2 + 2 a ( x- v t ) = 6 . 08475 m / s . 003 (part 1 of 2) 10.0 points A speeder passes a parked police car at a constant speed of 28 . 6 m / s. At that instant, the police car starts from rest with a uniform acceleration of 2 . 62 m / s 2 ....
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- Spring '08