HW_6 - its blades as it spins(a When the rotor faces...

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Physics 112 Homework #6 Fall 2006 Read: Chapter 6 For discussion: Chapter 6: Qs #6.1, 6.2, 6.3, 6.4, 6.6, 6.7, 6.10, 6.11, 6.12, 6.16, 6.17, 6.19, 6.20 (not turned in) Chapter 6: Es & Ps: #6.1, 6.7, 6.9, 6.11, 6.25, 6.27, 6.29, 6.33, 6.39, 6.43, 6.45, 6.49, 6.52, 6.73, 6.79, 6.81, 6.87, 6.97 Due Friday, Oct 6th at lecture: #6.25 [Little Red Wagon] #6.24[Watermelon] Please add: (c) What is the watermelon's speed just before it hits the ground according to work-energy considerations? #6.54 [Instantaneous Power] 1. Wind energy. The rotor blades of a certain wind turbine have a length L = 4.0 m (13 ft). The swept area of the rotor is the area of the circle of radius L swept out by
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Unformatted text preview: its blades as it spins. (a) When the rotor faces directly into a 20 mi/h (8.9 m/s) wind, what volume of air (in m 3 ) passes through the rotor's swept area in one second? (b) What is the mass of this amount of air (in kg)? (The density of air is 1.2 kg/m 3 .) (c) What is the total kinetic energy in this amount of air? (d) If the wind turbine has an efficiency of 45% for converting kinetic energy of the wind blowing through it into electrical energy, what is its maximum electric power output in this 20 mi/h wind (in kW)? (e) If the wind speed were to decrease by a factor of 1/2 to 10 mi/h, by what factor would the wind generator's electrical power output decrease? L...
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This note was uploaded on 08/12/2008 for the course PHYS 1112 taught by Professor Leclair,a during the Fall '07 term at Cornell.

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