Fa07-MT1-Huang-Exam

# Fa07-MT1-Huang-Exam - University of California, Berkeley...

This preview shows pages 1–2. Sign up to view the full content.

University of California, Berkeley Physics 7B, Fall 2007 ( Xiaosheng Huang ) Midterm 1 Tuesday, 10/2/2007 6:00-8:00 PM Fundamental Constants: Avogadro's number, N A : 6.02×10 23 Gas Constant, R : 8.315 J/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 1) (20 pts.) The density of atoms, mostly hydrogen, in interstellar space is about one per cubic centimeter. The temperature of this gas is ~3000 K. The diameter of a hydrogen atom is approximately 10 -10 m. Assume that the ideal gas law holds. a ) Estimate the pressure of this gas and express the pressure in torr. (1 atm=760 torr=1.01x10 5 Pa) b ) Estimate the mean free path. (You do not have to derive the expression for the mean free path.) 2) (30 pts.) A real heat engine working between heat reservoirs at T L =350K and T H =900K produces 700J of work per cycle for a heat input of 1800J. a

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

## This note was uploaded on 02/04/2010 for the course PHYSICS 7B taught by Professor Packard during the Spring '08 term at Berkeley.

### Page1 / 2

Fa07-MT1-Huang-Exam - University of California, Berkeley...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online