thy - bello (rtb473) hw14 Demkov (59910) This print-out...

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bello (rtb473) – hw14 – Demkov – (59910) 1 This print-out should have 40 questions. Multiple-choice questions may continue on the next column or page – fnd all choices beFore answering. 001 10.0 points Why do ice cubes ±oat? 1. Ice cubes are less dense than water. cor- rect 2. Ice cubes are in a solid state. 3. Ice cubes are lighter than water. Explanation: Ice cubes are less dense than water. IF ice were more dense than water, it would sink, and the bottom oF ponds and oceans could be covered by ice during the winter. 002 10.0 points When an air bubble rises in water, what hap- pens to its mass, volume, and density? 1. Volume doesn’t change; mass and desnisty increase. 2. Volume doesn’t change; mass and density decrease. 3. Mass doesn’t change; volume increases and density decreases. correct 4. All three are conserved. 5. Density doesn’t change; mass and volume decrease. 6. Density doesn’t change; mass and volume increase. 7. Mass doesn’t change; volume decreases and density increases. Explanation: d = m V The mass will not change (Boyle’s Law). The bubble’s pressure decreases so its vol- ume increases and the density decreases (same mass, smaller volume). 003 (part 1 oF 2) 10.0 points Calculate the ±ow rate oF blood (oF density 1 . 58 g / cm 3 ) in an aorta with a cross-sectional area oF 2 . 82 cm 2 iF the ±ow speed is 24 . 8 cm / s. Correct answer: 110 . 499 g / s. Explanation: Let : ρ = 1 . 58 g / cm 3 , A = 2 . 82 cm 2 , and v = 24 . 8 cm / s . ²low Rate = m t = m v d = ρ V v d = ρ A v = (1 . 58 g / cm 3 ) (2 . 82 cm 2 ) (24 . 8 cm / s) = (1 . 58 g / cm 3 ) (69 . 936 cm 3 / s) = 110 . 499 g / s . 004 (part 2 oF 2) 10.0 points Assume the aorta branches to Form a large number oF capillaries with a combined cross- sectional area oF 4480 cm 2 . What is the ±ow speed in the capillaries? Correct answer: 0 . 0156107 cm / s. Explanation: Let : A = 4480 cm 2 . ²rom the equation oF continuity, we have v = A A v = p 2 . 82 cm 2 4480 cm 2 P (24 . 8 cm / s) = 0 . 0156107 cm / s . 005 10.0 points The approximate inside diameter oF the aorta
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bello (rtb473) – hw14 – Demkov – (59910) 2 is 1 . 5 cm, and that of a capillary is 1 . 1 × 10 6 m. The average Fow speed is about 1 . 0 m/s in the aorta and 1 . 0 cm/s in the capillaries. If all the blood in the aorta eventually Fows through the capillaries, estimate the number of capillaries in the circulatory system. Correct answer: 1 . 8595 × 10 10 . Explanation: Basic Concepts: A c,tot v c = A a v a A c,tot = N A c A = πr 2 Given: r a = 1 . 5 cm 2 = 0 . 75 cm r c = 1 . 1 × 10 6 m 2 = 0 . 55 × 10 6 m v a = 1 . 0 m / s v c = 1 . 0 cm / s Solution: A c,tot = A a v a v c N ( π r 2 c ) = ( π r 2 a ) v a v c N = r 2 a v a r 2 c v c N = (0 . 75 cm) 2 (1 m / s) (5 . 5 × 10 7 m) 2 (1 cm / s) p 1 m 100 cm P = 1 . 8595 × 10 10 capillaries 006 10.0 points A water hose 2 . 81 cm in diameter is used to ±ll a 25 L bucket.
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This note was uploaded on 12/28/2008 for the course PHY 301 taught by Professor Swinney during the Spring '07 term at University of Texas at Austin.

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thy - bello (rtb473) hw14 Demkov (59910) This print-out...

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