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Unformatted text preview: ikram (ai2734) hw1001 Swinney (58785) 1 This print-out should have 7 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. Please study any test problems that you missed and discuss them with an instructor (LA, TA, Swinney) at office hours. 001 10.0 points The amount of work done by two boys who apply 300 N of force in an unsuccessful at- tempt to move a stalled car is 1. 600 N. 2. 300 N m. 3. 0. correct 4. 300 N. 5. 600 N m. Explanation: W = F d , so with an unsuccessful attempt to move the car, no work was done. 002 10.0 points At a certain point, when a spring is stretched near its elastic limit, the spring force satisfies the equation F =- x + x 3 , where = 14 N / m and = 13000 N / m 3 . Calculate the work done by the spring when it is stretched from its equilibrium position to . 042 m past its equilibrium. Correct answer:- 2 . 23499 mJ. Explanation: The work done is found by integrating the force of the spring over the distance it is com- pressed: W = integraldisplay x f x i F dx . For this problem W = integraldisplay x f x i (- x + x 3 ) dx . Evaluating the integral (where x i = 0) we find W =- x 2 f 2 + x 4 f 4 =- (14 N / m) (0 . 042 m) 2 2 + (13000 N / m 3 ) (0 . 042 m) 4 4...
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- Spring '07