Recent content by jdlawlis

  1. J

    Recommended books on relativity

    Great suggestions, Nugatory and Daverz!
  2. J

    Somewhat Rigorous thermodynamics?

    I have found Gaskell's "Introduction to Metallurgical Thermodynamics" to be excellent, with clear sections on statistical thermodynamics and excellent sections on entropy changes due to phase mixing, and a mathematical treatment of everything from integrating the specific heat with respect to...
  3. J

    Recommended books on relativity

    Dear Physics Forum community, I teach AP Physics and general physics at a small independent school. One of my colleagues asked me if I could recommend a book on relativity for the son of a friend, who is a bright 11th grade student. Sadly, I have not read many books in the popular science...
  4. J

    Effect of Moon's Orbital Speed on Frequency of Solar Eclipses

    I guess I'll answer my own question. According to the authors of the textbook, they subcontract the review questions/conceptual self-test questions at the end of each chapter to other people. It looks likely that there may be an error in the solution set.
  5. J

    Effect of Moon's Orbital Speed on Frequency of Solar Eclipses

    A question from Chaisson & McMillan's "A Beginner's Guide to the Universe" is as follows: If the Moon orbited Earth twice as fast, but in the same orbit, the frequency of solar eclipses would (a) double; (b) be cut in half; (c) stay the same. The answer key states that the correct answer...
  6. J

    Introductory Astronomy textbook

    I teach a semester-long Astronomy elective for juniors and seniors at an independent college preparatory high school. For the past few years, I have used Chaisson and McMillan's Astronomy: A Beginner's Guide to the Universe, which has served my purposes well. The course will be changing so...
  7. J

    Solving PV=nRT for Solids - How to Determine Temp?

    See http://en.wikipedia.org/wiki/Birch–Murnaghan_equation_of_state
  8. J

    What is the Error in My Derivation of the Dry Adiabatic Lapse Rate?

    I am aware of the derivation for the dry adiabatic lapse rate using the enthalpy approach: ncpdT+VdP=0, but I can't seem to spot the error in my own derivation. If anyone sees it, I would be especially grateful. dU=\deltaQ-\deltaW ncvdT=0 - PdV \frac{dT}{dV}=-\frac{P}{nc_{v}}...
  9. J

    Does Miskolczi's Paper Refute the Current Math of Greenhouse Effect?

    Error on page 4 Awww, this one's an easy one. There may be other mistakes, but clearly the author errs in point (g) on page 4. While the atmosphere is gravitationally bound to Earth, it does not orbit the Earth, in the sense that its kinetic energy is half the gravitational potential energy...
  10. J

    How Does Mass Affect Stellar Luminosity and Simulations?

    Thanks for your help. I should have clarified at the beginning that I was talking about main sequence stars.
  11. J

    How Does Mass Affect Stellar Luminosity and Simulations?

    In one of my textbooks, the authors claim that luminosity depends on the cube of the mass, yet several online resources say that luminosity varies as mass to the fourth power. Which one is correct?
  12. J

    Professional development for an AP Teacher

    I haven't posted here in a while, and it feels good to be back. Here's my dilemma. I have taught AP Mechanics and Electricity & Magnetism at a private school for a few years now. My background is not in Physics, however, and therefore I have not taken some of the standard courses that a...
  13. J

    Lenticular Galaxy - Formula for Probable Location of Stars

    Chaisson and McMillan's Astronomy textbook gives the following explanation for the strong magnetic fields in neutron stars: "The original field of the parent star is amplified as the collapsing core squeezes the magnetic field lines closer together, creating a magnetic field trillions of...
  14. J

    What is the force needed to make the wedge move?

    solution In this problem you have three unknown normal forces, three unknown friction forces and one unknown applied force P. You will get two equations for the x and y components of the net force on the ball, two equations for the x and y components of the net force on the wedge, one equation...
  15. J

    About how to prevent being struck by lightning

    potential difference during lightning strikes Richard Feynman has a good discussion of thunderstorms in his three volume Lectures on Physics (see Volume 2, Chapter 9). He estimates that the charge on the bottom of a cloud during a thunderstorm is large enough to produce a potential difference...
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