# Hw1 - sousse(res2468 – HW 1 – Kleinman –(58225 1 This print-out should have 10 questions Multiple-choice questions may continue on the next

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Unformatted text preview: sousse (res2468) – HW 1 – Kleinman – (58225) 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 An acceleration of 3 mi / h / s is equal to Correct answer: 1 . 34083 m / s 2 . Explanation: Let : a = 3 mi / h / s . a = 3 mi h · s · 1 . 609 km 1 mi · 1000 m 1 km · 1 h 3600 s = 1 . 34083 m / s 2 . 002 10.0 points A cylinder, 18 cm long and 6 cm in radius, is made of two different metals bonded end-to- end to make a single bar. The densities are 4 . 9 g / cm 3 and 6 . 5 g / cm 3 . 1 8 c m 6 cm , radius What length of the lighter-density part of the bar is needed if the total mass is 11212 g? Correct answer: 11 . 1651 cm. Explanation: Let : ℓ = 18 cm , r = 6 cm , ρ 1 = 4 . 9 g / cm 3 , ρ 2 = 6 . 5 g / cm 3 , and m = 11212 g . Volume of a bar of radius r and length ℓ is V = π r 2 ℓ and its density is ρ = m V = m π r 2 ℓ so that m = ρ π r 2 ℓ ℓ x ℓ- x r Let x be the length of the lighter metal; then ℓ- x is the length of the heavier metal. Thus, m = m 1 + m 2 = ρ 1 π r 2 x + ρ 2 π r 2 ( ℓ- x ) = ρ 1 π r 2 x + ρ 2 π r 2 ℓ- ρ 2 π r 2 x. Therefore m- ρ 2 π r 2 ℓ = ρ 1 π r 2 x- ρ 2 π r 2 x and xπ r 2 ( ρ 1- ρ 2 ) = m- ρ 2 π r 2 ℓ . Consequently, x = m- ρ 2 π r 2 ℓ π r 2 ( ρ 1- ρ 2 ) = (11212 g)- (6 . 5 g / cm 3 ) π (6 cm) 2 (18 cm) π (6 cm) 2 (4 . 9 g / cm 3- 6 . 5 g / cm 3 ) = 11 . 1651 cm . 003 10.0 points A piece of pipe has an outer radius, an in- ner radius, and length as shown in the figure below. sousse (res2468) – HW 1 – Kleinman – (58225) 2 3 9 c m 4 . 7 cm...
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## This note was uploaded on 04/08/2009 for the course PHY 303K taught by Professor Turner during the Spring '08 term at University of Texas at Austin.

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Hw1 - sousse(res2468 – HW 1 – Kleinman –(58225 1 This print-out should have 10 questions Multiple-choice questions may continue on the next

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