Sp09-MT1-Huang-Exam

# Sp09-MT1-Huang-Exam - University of California Berkeley...

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University of California, Berkeley Physics 7B, Lecture 001, Spring 2009 ( Xiaosheng Huang ) Midterm 1 Monday, 2/23/2009 6:00-8:00 PM Name:______________________ SID: ________________________ D/L Section:_______________ GSI: ________________________ Physical Constants: Avogadro's number, N A : 6.02 × 10 23 Gas Constant, R : 8.315J/mol·K Boltmann's Constant, k B : 1.38 × 10 -23 J/K Stefan-Boltzmann Constant, σ : 5.67 × 10 -8 W/m 2 ·K 4 Specific heat for water: c =4.19 × 10 3 J/kg· o C Heat of vaporization for water: L V =22.6 × 10 5 J/kg Heat of fusion for water: L F = 3.33 × 10 5 J/kg Standard Temperature and Pressure (STP): T =273K, P =1atm=1.01 × 10 5 Pa Atomic mass unit (1u): 1.6605 × 10 -27 kg Note : You are allowed one formula sheet (3 ½ by 5, double sided) and a calculator (without wireless capabilities). Do NOT just write down an answer in the answer box; show your steps. Formulaic answers may only involve the quantities given in a problem and constants. Good Luck! #1 #2 #3 #4 Total

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1. (25 pts.) A spherical solid aluminum sphere with mass M , density ρ , specific heat c , and emissivity e , floats in the vacuum of intergalactic space. The sphere is initially ( t =0) at temperature T 1 . a) How long does it take for the aluminum sphere to cool to the cosmic microwave background (CMB) temperature, T 0 , assuming T 1 > T 0 ? (For this part, ignore the radiation energy that the aluminum sphere will absorb from the (CMB)).
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Sp09-MT1-Huang-Exam - University of California Berkeley...

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