HW10 - Sound Waves Begin Date: 11/16/2017 12:01:00 AM - - Due Date: 11/30/2017 8
ID: 1795369 • Letter: H
Question
HW10 - Sound Waves Begin Date: 11/16/2017 12:01:00 AM - - Due Date: 11/30/2017 8:00:00 AM End Date: 12/10/2017 11:59:00 PM (10%) Problem 2: A periodic vibration at x=0, t= 0 displaces air molecules along the x direction by smax 4.9E-05 m. The motion produces a sound wave that travels at a velocity of v-333 ms with a frequency of 140 Hz. Take the density of air as ,-1.20 kg/m, max ©theexpertta.com -.. 14% Part (a) Calculate the wavelength of the sound wave, in meters Grade Summary Deductions Potential 0% 100% sin0 cotan0asin acos0 atan0 acotan sinhO cosh0 tanh cotanh0 cos) tan Submissions Attempts remaining: 3 (400 per attempt) detailed view END Degrees Radians Submit Hint I give up! Hints: 4% deduction per hint. Hints remaining: 2 Feedback: 5% deduction per feedback. - 14% Part (c) Calculate the angular frequency of the sound , in radians per second at time t = 0.001 s and displacement x = 1.0 m. velocity v, the angular frequency a, and the maximum displacement smax 14% Part (b) Calculate the wavenumber k of the sound, in radians per meter 14% Part (d) Calculate the displacement of the air molecules using an function for the traveling sound wave in terms of time and position 14% Part (e) Write an expression for the maximum pressure exerted by the sound wave Amax in terms of the air density a the sound 14% Part (f) The sound wave is directly incident on a sheet of paper of surface area.4 = 0.013 mCalculate the maximum force F a in 14% Part (g) If the frequency of the sound wave were increased by a factor of 100, how would the force exerted on the sheet in part (f) , newtons, exerted on this sheet. change?Explanation / Answer
a) use, lmada = v/f
= 333/140
= 2.38 m
b) k = 2*pi/lamda
= 2*pi/2.38
= 2.64 rad/m
c) w = 2*pi*f
= 2*pi*140
= 880 rad/s
d) at t = 0.001 s, x = 1 m
use, x = S_max*cos(k*x - w*t)
= 4.9*10^-5*cos(2.64*1 - 880*0.001)
= -0.92*10^-5 m
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