Question
help #5,6,7,8 asap please, Thank you
3. y-6 sin(2 t-5x). U eer-5 Velocity ofpropag ation of the wave is bme A) 12 B) 2 C)2.4 DI4 E) 2.5 4. Diatomic hydrogen explodes adiabustically to 34 times its original volume before is pressure reduces back to atmospheric pressure. When ignited, what was its initial pressure? ri vw: A) 79.3 Atm B) 102.34 Atm C)'1393 Atm D) 10.2 Atm E) 306 Am 5. The tungsten manent ora lighibulb has ar, openting tumperatin ofabott 2700 wten the poem semprareis 200: Ifthe emining ares of the flament is 1.I cmi, and its enisiity is 0.6, whet is the pesar osipet of the lightblbSepha-Bota Constant-567 x 10 wmK') A) 16.2 Watts B) 27621 Watts C) 37.26 Watts D) 49.5 Watts E) 29.23 Watts 6. What is the entropy change for7rolesofa poly on ideal gas isobanc process from 23 ' to 10007 froau 23 C to 100 *C7 A) 53.83 J/K B) 193/K C) 161 JK D) 48.3 IK E) 703k 7. A 300 Hz siren is moving at 90 f's toward a person running away from it at 20 s. What pitch does the person A) 120 Hz B) 320.8 Hz C) 135Hz D) 1080 E)600 Hz hear? (Vesnd-1100 f's) &. A 3 loop string has a linear mass density of 28 grams'em and a length of T0 cm. If the tension in the sarimg is 19 N, at what frequency is the string vibrating? A A) 5582 Hz B) 57 Hz C) 11.1 Hz D) 693 E) 171 09.3 E) 171 Hz If the distance between a point sound source and a dB detector is Incressed by a factor of8, wh will be 'he reducion a iracesny n28 872 N B) 10.9 N C) 21.12 N D) 7.04 N(E)8.06 N&W;: ro ipo-: level? Cy
Explanation / Answer
5. given, emissivity, e = 0.6
filament area, A = 1.1 cm^2
power emitted , Pe = sigma*A*e*Te^4
POWER ABSORBED, Pa = sigma*A*e*To^4
Te = 2700 C = 2700 + 273.16 = 2973.16 K
To = 20 C = 293.16 K
Net power emitted = sigma*A*e*(Te^4 - To^4) [ sigma is stefans constant]
P = 276.21 Watts
6. For isobaric process, dS = Cp*ln(T2/T1)
Cp for polyatomic ideal gas = 9R/2 = 9*8.314/2 = 37.413
so Entropy change for n moles = Cp*n*ln(T2/T1) = 37.413*7*ln([100+273.16]/[23 + 273.16]) = 70 J/K option E
7. for source moving towards the observer and observer moving away from the source
f = (c - vr)fo/(c - vs)
c = 1100 f/s
vr = 20 ft/s
vs = 90 ft/s
fo = 300 Hz
f = (1100 - 20)300/(1100 - 90) = 320.79 Hz ( option B)
8. given, rho = .28 grams/cm
l = 70 cm
T = 19 N
so, speed of wave, c = l*f/2
f = 2c/l
but c = sqroot(T/mu)
so f = 69.3 Hz
