# quiz919 - Version 055/AADBD quiz919 Demkov(59910 This...

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Version 055/AADBD – quiz919 – Demkov – (59910) 1 This print-out should have 5 questions. Multiple-choice questions may continue on the next column or page – fnd all choices beFore answering. 001 10.0 points A boat moves through the water oF a river at 7 . 78 m / s relative to the water, regardless oF the boat’s direction. IF the current is ±owing at 5 . 15 m / s, how long does it take the boat to complete a trip consisting oF a 234 m displacement down- stream Followed by a 239 m displacement up- stream? 1. 482.096 2. 256.286 3. 219.423 4. 75.8412 5. 108.972 6. 115.74 7. 225.913 8. 201.502 9. 133.677 10. 302.569 Correct answer: 108 . 972 s. Explanation: Let v b be the velocity oF the boat relative to the water, and v w the velocity oF water relative to the shore. Take downstream as the positive direction. ²or the downstream trip, the current is speeding him up, so the velocity oF the boat relative to the shore is v d = v b + v w and the time is t d = x d v d = x d v b + v w ²or the upstream trip, the current is slowing him down, so the velocity oF the boat relative to the shore is v u = v b - v w and the time is t u = x u v

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## This note was uploaded on 11/01/2008 for the course PHY 301 taught by Professor Swinney during the Spring '07 term at University of Texas.

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quiz919 - Version 055/AADBD quiz919 Demkov(59910 This...

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