# HW1 - muir(cem2577 HW1 Niu(58205 This print-out should have...

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muir (cem2577) – HW1 – Niu – (58205) 1 This print-out should have 26 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 The rectangular and polar coordinates oF a point are ( x, y ) and ( r, θ ), where x = 6 and θ = 16 . Determine the value oF r. Correct answer: 6 . 2418. Explanation: The relation between rectangular and polar coordinates is: x = r cos θ y = r sin θ solving For r, r = x cos θ = 6 cos(16 ) = 6 . 2418 002 (part 2 oF 2) 10.0 points Determine the value oF y. Correct answer: 1 . 72047. Explanation: y = r sin θ = (6 . 2418) sin(16 ) = 1 . 72047 003 10.0 points A human hair is approximately 54 μ m in di- ameter. Express this diameter in meters. Correct answer: 5 . 4 × 10 5 m. Explanation: Basic Concept: 1 μ m = 1 × 10 6 m Let: diameter = 54 μ m Solution: diameter = 54 μ m = ( 5 . 4 × 10 1 μ m ) · 1 × 10 6 m 1 μ m = 5 . 4 × 10 5 m keywords: /* IF you use any oF these, fx the comment symbols. 004 10.0 points The modern standard oF length is 1 m and the speed oF light is approximately 2 . 99792 × 10 8 m / s . ±ind the time Δ t For light to cover 1 m at the given speed. 1. Δ t 3 . 3 × 10 8 s 2. Δ t 3 . 3 × 10 7 s 3. Δ t 3 × 10 6 s 4. Δ t 3 × 10 8 s 5. Δ t 3 . 3 × 10 6 s 6. Δ t 3 . 3 × 10 9 s correct 7. Δ t 3 × 10 10 s 8. Δ t 3 × 10 7 s 9. Δ t 3 × 10 9 s 10. Δ t 3 . 3 × 10 10 s Explanation: Since distance is speed times velocity, we have speed = distance time . ±rom the relationship oF speed to distance and time, we get Δ t = distance speed = d c = 1 m 2 . 99792 × 10 8 m / s = 3 . 33564 × 10 9 s .

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muir (cem2577) – HW1 – Niu – (58205) 2 005 10.0 points The standard of time is based on 1. a precision pendulum clock. 2. the frequency of light emitted by 86 Kr. 3. the daily rotation of the earth. 4. the yearly revolution of the earth about the sun. 5. None of these correct Explanation: The second is deFned from oscillations of cesium-133 atoms. 006 10.0 points A gram is 1. 10 6 kg 2. 1 kg 3. 10 3 kg 4. 10 6 kg 5. 10 3 kg correct Explanation: A kg is the notation for a kilogram, and kilo refers to 1000, or 10 3 , hence 1 g = 10 3 kg. 007 10.0 points You can obtain a rough estimate of the size of a molecule by the following simple exper- iment. Let a droplet of oil spread out on a smooth water surface. The resulting oil slick will be approximately one molecule thick. Given an oil droplet of mass of 8 . 67 × 10 7 kg and density of 930 kg / m 3 that spreads out into a circle of radius 36 . 7 cm on the water surface, estimate of magnitude of the diameter of an oil molecule. Correct answer: 2
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HW1 - muir(cem2577 HW1 Niu(58205 This print-out should have...

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