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solution30 - fullwood (tf5349) Homework # 3 Motion Catala...

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fullwood (tf5349) – Homework # 3 Motion – Catala – (49033) 1 This print-out should have 20 questions. Multiple-choice questions may continue on the next column or page – Fnd all choices before answering. 001 (part 1 of 2) 10.0 points A car with an initial speed of 21.1 km/h ac- celerates at a uniform rate of 0.88 m/s 2 for 4.7 s. ±ind the Fnal speed of the car. Correct answer: 9 . 99711 m / s. Explanation: Let : v i = 21 . 1 km / h , a = 0 . 88 m / s 2 and Δ t = 4 . 7 s . v f = v i + a Δ t = (21 . 1 km / h) · 1000 m 1 km · 1 h 3600 s + (0 . 88 m / s 2 )(4 . 7 s) = 9 . 99711 m / s 002 (part 2 of 2) 10.0 points ±ind the displacement of the car after that time. Correct answer: 0 . 0372668 km. Explanation: Δ x = v i Δ t + 1 2 a t ) 2 = (21 . 1 km / h)(4 . 7 s) · 1 h 3600 s + 1 2 ( 0 . 88 m / s 2 ) (4 . 7 s) 2 1 km 1000 m = 0 . 0372668 km 003 10.0 points When the shuttle bus comes to a sudden stop to avoid hitting a dog, it decelerates uniformly at 5.4 m/s 2 as it slows from 9.4 m/s to 0 m/s. ±ind the time interval of acceleration for the bus. Correct answer: 1 . 74074 s. Explanation: Let : a avg = - 5 . 4 m / s 2 , v i = 9 . 4 m / s , and v f = 0 m / s . a avg = Δ v Δ t = v f - v 0 Δ t = - v 0 Δ t Δ t = - v i a avg = - 9 . 4 m / s - 5 . 4 m / s 2 = 1 . 74074 s . 004 10.0 points A worker drops a wrench from the top of a tower 61.0 m tall. What is the velocity when the wrench strikes the ground? Correct answer: - 34 . 5951 m / s. Explanation: Basic Concept: When v i = 0 m/s, the equation simpliFes to v 2 f = 2 a Δ y Given: v i = 0 m / s Δ y = - 61 . 0 m a = - 9 . 81 m / s 2 Solution: v f = ± r 2 a Δ y = ± R 2( - 9 . 81 m / s 2 )( - 61 m) = ± 34 . 5951 m / s Since the wrench is moving downwards, v f = - 34 . 5951 m / s.
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fullwood (tf5349) – Homework # 3 Motion – Catala – (49033) 2 005 10.0 points A baby sitter pushing a stroller starts from rest and accelerates uniformly at a rate of 0.657 m/s 2 . What is the velocity of the stroller after it has traveled 7.14 m? Correct answer: 3
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This note was uploaded on 06/10/2010 for the course PHY 100 taught by Professor Pro.kiroshima during the Spring '10 term at Adelphi.

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solution30 - fullwood (tf5349) Homework # 3 Motion Catala...

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