y = 6 sin(3t - 9x). Velocity of propagation of A) 3 B) 3 C) 0.333 D) 1 E) 3.6 Wh
ID: 1645342 • Letter: Y
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y = 6 sin(3t - 9x). Velocity of propagation of A) 3 B) 3 C) 0.333 D) 1 E) 3.6 What is the root mean square velocity of gasX molecules at a temperature of 65 degree C? (R = 8.314 J/mole-K, N_A = 6.02 times 10^23, and the molecular mass of gasX=55 grams) A) 269.1 m/s B) 213 m/s C) 3575 m/s D) 391.5 m/s E) 1179.75 m/s A very loud train whistle has an acoustic power output of 100 watts. If the sound energy spreads out spherically, what is the intensity level in dB at a distance of 95 meters from the train? (I_0 = 10^-12 Watts/m^2) A) 51.6 dB B) 86 dB C) 178.6 dB D) 110 dB E) 89.45 dB A 3 loop string has a linear mass density of 28 grams/cm and a length of 135 cm. If the tension in the string is 19 N, at what frequency is the string vibrating? A) 171 Hz B) 28.94 Hz C) 57 Hz D) 21.3 Hz E) 133.65 Hz If the distance between a point sound source and a dB detector is increased by a factor of 6, what will be the reduction in intensity level? A) 17.28 N B) 15.56 N C) 5.76 N D) 7.56 N E) 21.762 N A mass on a spring vibrates in simple harmonic motion at a frequency of 3 Hz and an amplitude of 8 cm. If a timer is started displacement is a maximum (hence x = 8 cm when t = 0), what is the displacement of the mass when t = 2.8 s? A) 7.2 cm B) 2.52 cm C) -8.57 cm D)-6.472 cm E) 2.333333 cmExplanation / Answer
Ans.(17)
power P = 100 W,
intensity I = P/area
= P/(4*pi*r^2)
=100/(4*pi*95^2)
= 8.81*10^-4 W/m2
intensity level in dB = 10log10(I/*10^-12)
=10log10(8.81*10^-4/10^-12)
= 89.45 dB
answer (E)
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