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# cw3 - patel(kp9583 CW3 Mackie(20211 This print-out should...

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patel (kp9583) – CW3 – Mackie – (20211) 1 This print-out should have 3 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. DEADLINE IS CENTRAL TIME! 001 10.0 points Two particles are at the same point at the same time, moving in the same direction. Par- ticle A has an initial velocity of 8 . 7 m / s and an acceleration of 2 . 9 m / s 2 . Particle B has an initial velocity of 2 . 5 m / s and an acceleration of 4 . 8 m / s 2 . At what time will B pass A? Correct answer: 6 . 52632 s. Explanation: Basic Concept: s = s 0 + v 0 t + 1 2 at 2 Solution: For particle A, s 0 A = 0, so s A = v 0 A t + 1 2 a A t 2 For particle B, s 0 B = 0, so s B = v 0 B t + 1 2 a B t 2 When B overtakes A, the positions are the same, so v 0 A t + 1 2 a A t 2 = v 0 B t + 1 2 a B t 2 2 v 0 A t + a A t 2 = 2 v 0 B t + a B t 2 a A t 2 - a B t 2 + 2 v 0 A t - 2 v 0 B t = 0 t ( a A t - a B t + 2 v 0 A - 2 v 0 B ) = 0 The solutions are t = 0 which tells us that they were at the same position when t=0 and ( a A - a B ) t + 2 ( v 0 A - v 0 B ) = 0 = t = 2 ( v 0 B - v 0 A ) a A - a B 002 10.0 points A ball is thrown upward.

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