Hw2 - Problem 1 Sllow t hat the quantity speed has the units of Problem 19 W hat is the approximate frequency ran e over which sound with intensity

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- -- Problem 1. Sllow that the quantity has the units of speed. Solution The units of pressure (force per unit area) divided by 3 density (mass per unit volome) are (~/m~)/(k~/m ) = (~/k~)(m~/m~) = (m/s2)m = (m/~)~, or those of speed squared. - - Problem 9. A gas with density 1.0 kg/m3 and pressure 8.0x104 iV/m2 has sound speed 365 m/s. Are the gas molecules monatomic or diatomic? Solution Solving for 7 in Equation 17-1, we find 7 = pv2/P = (1.0 kg/m3)(365 m/s)*/(8.0~10' ~/m~) = 1.67, very close to the value for an ideal monatomic gas. (Actually, 7 - 513 = -1.35~10-~ for this gas.) -. Problem 15. Sound intensity in normal conversation is about 1 pw/m2. What is the displacement amplitude of air in a 2.5-kHz sound wave with this intensity? Solution As in Example 17-2, Equation 17-3c, combined with the atmospheric data in Example 17-1, can be used to calculate the displacement amplitude for sound waves of the specified frequency and intensity: 2(10-6 w/m2) = 4.44 nm. (1.20 kg/m3) (343 m/s) - Problem 18. A "tweeter" loudspeaker emitting 5.0 kHz sound has an oscillation amplitude of 1 pm. What must be the oscillation amplitude of a "woofer" speaker producing the same sound intensity at 30 Hz? Solution For the same same air, Equation 17-3c constant. Therefore, a comparison of the woofer and tweeter yields (so), = ' (SO)~W*/W~ = (1 pm)(5 kHz/30 Hz) = 167 pm.
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This note was uploaded on 12/03/2009 for the course PHYS 2c taught by Professor Wurthmeir during the Spring '05 term at UCSD.

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Hw2 - Problem 1 Sllow t hat the quantity speed has the units of Problem 19 W hat is the approximate frequency ran e over which sound with intensity

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