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HW02-solutions

# HW02-solutions - sela(ds39632 HW02 janow(11196 This...

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sela (ds39632) – HW02 – janow – (11196) 1 This print-out should have 9 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 10.0points A car travels along a straight stretch of road. It proceeds for 17 . 7 mi at 52 mi / h, then 24 mi at 46 mi / h, and finally 37 . 4 mi at 31 . 1 mi / h. What is the car’s average velocity during the entire trip? Correct answer: 38 . 3107 mi / h. Explanation: Let : d A = 17 . 7 mi , v A = 52 mi / h , d B = 24 mi , v B = 46 mi / h , d C = 37 . 4 mi , and v C = 31 . 1 mi / h . The total time the car spent on the road is Δ t = d A v A + d B v B + d C v C = 17 . 7 mi 52 mi / h + 24 mi 46 mi / h + 37 . 4 mi 31 . 1 mi / h = 2 . 0647 h , so the average velocity is v = Δ d Δ t = d A + d B + d C Δ t = 17 . 7 mi + 24 mi + 37 . 4 mi 2 . 0647 h = 38 . 3107 mi / h . 002 10.0points The velocity of a particle moving along the x axis varies in time according to the expression v ( t ) = α + β t 2 where α = 42 . 6 m / s, β = 4 . 02 m / s 3 , and t is in seconds. Find the average acceleration in the time interval from t = 0 to 3 . 53 s. Correct answer: 14 . 1906 m / s 2 . Explanation: The velocities at t i = 0 and t f = 3 . 53 s are found by substituting these values into the expression given for the velocity: v i = α + β t 2 i = 42 . 6 m / s + (4 . 02 m / s 3 ) (0 s) 2 = 42 . 6 m / s

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