Recent content by jdlawlis

  1. J

    What Are the Best Books on Relativity for High School Students?

    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

    What Are the Best Books on Relativity for High School Students?

    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

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

    See http://en.wikipedia.org/wiki/Birch–Murnaghan_equation_of_state
  7. 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}}...
  8. 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...
  9. 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.
  10. 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?
  11. 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...
  12. 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...
  13. 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...
  14. J

    Checking thermocouple knowledge

    I wouldn't recommend Cu extension wires Thermocouples work on the principle of having two dissimilar metals at unknown temperature (the measuring temperature) and at known temperature (the cold junction). By introducing copper into the mix, you are creating two additional junctions (for K-type...
  15. J

    Historical question concerning Moseley's experiment

    This question may be beyond the scope of this forum, but I'll give it a go anyway. Moseley's landmark experiments in 1913 related the square root of the frequency of characteristic X-rays of an element to integer values, which he equated to the element's atomic number. He measured the...
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