ohw 15 - brown(twb493 ohw 15 turner(57340 This print-out...

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brown (twb493) – ohw 15 – turner – (57340) 1 This print-out should have 10 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 oF weight 2100 N operating at a rate oF 106 kW develops a maximum speed oF 26 m / s on a level, horizontal road. Assuming that the resistive Force (due to Friction and air resistance) remains constant, what is the car’s maximum speed on an incline oF 1 in 20; i.e. , iF θ is the angle oF the incline with the horizontal, sin θ = 1 / 20 ? Correct answer: 25 . 3472 m / s. Explanation: IF f is the resisting Force on a horizontal road, then the power P is P = f v horizontal . so that f = P v h = 1 . 06 × 10 5 W 26 m / s = 4076 . 92 N . On the incline, the resisting Force is F = f + mg sin θ = f + W 20 = P v h + W 20 . And, F v = P , so v = P F = P P v h + W 20 = 1 . 06 × 10 5 W 1 . 06 × 10 5 W 26 m / s + 2100 N 20 = 25 . 3472 m / s . 002 (part 2 of 2) 10.0 points What is its power output on a 1-in-10 incline iF the car is traveling at 16 m / s? Correct answer: 68590 . 8 W. Explanation: On the reduced incline, we again have, P = F v = ( f + m g sin θ ) v The only change From the previous problem is sin θ = 1 10 , so P = p f + W 10 P v = p p v h + W 10 P v = p 1 . 06 × 10 5 W 26 m / s + 2100 N 10 P (16 m / s) = 68590 . 8 W . 003 10.0 points A certain waterFall is 122 . 9 m high and has water ±ow rate oF 33 . 9 m 3 / s. The acceleration oF gravity is 9 . 8 m / s 2 . ²ind the maximum electric power that can be generated by these Falls assuming 100% conversion oF mechanical energy to electric energy. (Take the density oF water to be 1 . 00 × 10 3 kg / m 3 ) Correct answer: 4 . 08298 × 10 7 W. Explanation: Basic Concepts: Potential Energy and Power Solution: When water Falls From a high place, its potential energy decreases; For the waterFall, the variation oF potential energy per second is Δ U = ( ρr ) g h = (1000 kg / m 3 ) (33 . 9 m 3 / s) × (9 . 8 m / s 2 ) (122 . 9 m) = 4 . 08298 × 10 7 J / s .

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brown (twb493) – ohw 15 – turner – (57340) 2 When converted into electric energy, the power is P = Δ U = 4 . 08298 × 10 7 W . 004
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ohw 15 - brown(twb493 ohw 15 turner(57340 This print-out...

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