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Unformatted text preview: armington (kma786) – hw0201 – fiete – (57165) 1 This print-out should have 15 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 10.0 points If you drop an object, it will accelerate down- ward at a rate of g = 9 . 8 m / s 2 . If you throw it downward instead, its accel- eration (in the absence of air resistance) will be 1. less than 9 . 8 m / s 2 . 2. 9 . 8 m / s 2 correct 3. greater than 9 . 8 m / s 2 . 4. Unable to determine. Explanation: The acceleration due to the gravity is in- dependent of any initial velocity and remains constant. 002 10.0 points A stone is thrown straight upward and at the top of its trajectory its velocity is momentar- ily zero. What is its acceleration at this point? 1. 9.8 m/s 2 down correct 2. Unable to determine 3. 9.8 m/s 2 up 4. Zero Explanation: The gravitational acceleration near the sur- face of the earth is considered constant for all practical purposes. This acceleration of 9.8 m/s 2 points downward. 003 10.0 points A basketball player achieves a hang time of . 94 s in dunking the ball. What vertical height will he attain? The acceleration of gravity is 9 . 8 m / s 2 . Correct answer: 1 . 08241 m. Explanation: Let : t = 0 . 94 s and g = 9 . 8 m / s 2 . It takes the basketball player Δ t = t 2 to rise to his maximum height, defined by h = 1 2 g (Δ t ) 2 = g 2 t 2 4 = g t 2 8 = (9 . 8 m / s 2 ) (0 . 94 s) 2 8 = 1 . 08241 m . 004 10.0 points The acceleration of a marble in a certain fluid is proportional to the speed of the marble squared, given by a = α v 2 , where v > 0 m/s and α =- 1 . 61 m − 1 . If the marble enters this fluid with a speed of 0 . 96 m / s, how long will it take before the marble’s speed is reduced to half of its initial value? Correct answer: 0 . 646998 s....
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This note was uploaded on 02/11/2011 for the course PHY 301 taught by Professor Swinney during the Spring '07 term at University of Texas.

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solution_3pdf - armington (kma786) – hw0201 – fiete –...

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