A vertical spring with a spring constant 36 N/m is hanging from a ceiling. A sma

Question

A vertical spring with a spring constant 36 N/m is hanging from a ceiling. A small object with a mass 2.3 kg is then attached. The object is then pulled down and released, The speed of the object when it is 10 cm from the equilibrium position is 1.9 m/s. How far down was the object pulled? A) 68.4 cm B) 43.6 cm C) 49.05 cm D) 23.184 cm E) 21.888 cm A very loud train whistle has an acoustic power output of 65 watts. If the sound energy spreads out spherically, what is the intensity level in dB at a distance of 105 meters from the train? (I_o = 101 Watts/m^2). A) 32.37 dB B) 86.71 dB C) 53.95 dB D) 82.2 dB E) 128.31 dB An increase of 50 dB increases the sound intensity by a factor of A) 1400 B) 200 C) 100000 D) 100 E) 3500 What is the entropy change for 6.5 moles of a polyatomic ideal gas isobaric process from 29 degree C to 190 degree C? A) 284.05 J/K B) 92.37 J/K C) 123.5 J/K D) 11.9 J/K E) 56.55J/K Diatomic hydrogen explodes adiabatically to 22 times its original volume before its pressure reduces back to atmospheric pressure. When ignited, what was its initial pressure? A) 18.92 Atm B) 75.75 Atm C) 330 Atm D) 8.8 Atm E) 11 Atm The density of a certain metal solid is 7.8 times 10 degree kg/m^3 and its Young's modulus is 1.4 times 10^11 N/m^2. What is the velocity of sound in this metal? A) 3494.4 m/s B) 4237 m/s C) 3978 m/s D) 3640 m/s E) 2457 m/s A 650 Hz siren is moving at 90 f/s toward a person running away from it at 10 f/s. What pitch does the person hear? (V_sound = 1100 f/s) A) 585 Hz B) 130 Hz C) 650 Hz D) 701.5 Hz E) 2340 Hz The tungsten filament of a lightbulb has an operating temperature of about 3300 degree C when the room temperature is 20 degree C. If the emitting area of the filament is 1.1 cm^2, and its emissivity is 0.5, what is the power output of the lightbulb? (Stephan-Boltzmann Constant-5.67 times 10^-8 W/m^2 K^4) A) 337.59 Watts B) 72.6 Watts C) 16.5 Watts D) 50.82 Watts E) 37.95 Watts Suppose the ends of a 26 m long steel beam are rigidly clamped at 0 degree C to prevent expansion. The rail has a cross-sectional area of 10 cm^2. What force does the beam exert when it is heated to 60 degree C? (alpha-alpha_steel = 1.1 times 10^-5 C degree, Y_steel = 2 times 10^11 N/m^2.) A) 1560 N B) 43680 N C) 4340 N D) 8060 N E) 13200 N A person in a parked car sounds the horn. The frequency of the horn's sound is 455 Hz. A driver in an approaching car measures the frequency of the horn's sound is 455 Hz. A drive in an approaching car measures the frequency of the horn's sound as 505 Hz. What is the speed of the approaching car? (Use 343 m/s for the speed of sound.) A) 42.9065 m/s B) 68.9325 m/s C) 37.69 m/s D) 16.8 m/s E) 46.6375 m/s

Explanation / Answer

11. total energy = k A^2 /2 = k x^2 /2 + m v^2 /2

36 A^2 = 36 (0.10^2) + (2.3)(1.9^2)

A = 0.4905 m Or 49.05 cm

ANs(C)

12. I = P / (4 pi r^2) = 65 / (4 x pi x 105^2)

I = 4.69 x 10^-4 W/m^2

Sound intensity = 10 log( 4.69 x 10^-12 / 10^-12)

= 86.71 dB

Ans(B)

13. SL1 - SL2 = 10 log(I1 / 10^-12) - 10 log(I2 / 10^-12)

50 = 10 log(I1 / I2)

I1 / I2 = 10^5

Ans(C)

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