HW2-solutions - Agha (sa9896) – HW2 – bohm – (59970)...

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Unformatted text preview: Agha (sa9896) – HW2 – bohm – (59970) 1 This print-out should have 10 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 10.0 points A car traveling at 7.0 m/s accelerates 3.5 m/s 2 to reach a speed of 12.0 m/s. How long does it take for this acceleration to occur? Correct answer: 1 . 42857 s. Explanation: Basic Concept: a avg = Δ v Δ t Given: v i = 7 . 0 m / s a avg = 3 . 5 m / s 2 v f = 12 . 0 m / s Solution: Δ t = Δ v a avg = v f − v i a avg = 12 m / s − 7 m / s 3 . 5 m / s 2 = 1 . 42857 s Dimensional analysis for Δ t : m s ÷ m s 2 = m s · s 2 m = s 002 10.0 points If your car goes from 0 mi / h to 70 mi / h in 5 s, what is your average acceleration? Correct answer: 14 miles h · s . Explanation: Δ v = a t , so a = Δ v t = v 2 − v 1 t = 70 mi / h − 0 mi / h 5 s = 14 mi h · s . 003 10.0 points A car, moving along a straight stretch of high- way, begins to accelerate at 0 . 0491 m / s 2 . It takes the car 74 . 9 s to cover 1 km. How fast was the car going when it first began to accelerate? Correct answer: 11 . 5123 m / s. Explanation: We can describe this situation with the equation d = v t + 1 2 at 2 Given the time, distance and acceleration we simply solve for the initial velocity v = d t − 1 2 at converting the distance from km to m to ob- tain the proper units....
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This note was uploaded on 11/03/2008 for the course PHY 302K taught by Professor Kaplunovsky during the Spring '08 term at University of Texas.

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HW2-solutions - Agha (sa9896) – HW2 – bohm – (59970)...

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