Assignment 7 spring 2012

# Hint what is the total kinetic energy at that instant

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Unformatted text preview: t: what is the total kinetic energy at that instant? Make a sketch.) 3. Why use electrons? Why not transmit power down power lines mechanically instead of electrically? Let's assume you send transverse waves down a 2 cm diameter power line that is made of an aluminum alloy with density 2700 kg/m3 and an ultimate strength (beyond which it fails) of 400 MPa. Neglect the line's weight, and assume that it is under a uniform tension corresponding to 1/10 its ultimate strength. We drive one end of the power line up and down at 60 Hz, launching a harmonic traveling wave of amplitude A. What must be the amplitude A for the average power transmitted by the wave to be (a) 1 MW and (b) 400 MW (more typical of large diameter, 765 kV power lines)? What would be the maximum transverse speed of the power line in (b)? (People who live near power lines tend to worry about possible ill effects. Would mechanical power transmission be likely to decrease or increase their concerns?) 4. Energy and Power in Sound Waves. Let'...
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## This note was uploaded on 02/27/2013 for the course PHY 2214 taught by Professor Davis during the Spring '12 term at Cornell University (Engineering School).

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