14 April 2014

Physics Homework Chapter 27

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I have lost all of the homework problems for this chapter.
I would like to post videos.
I created the calculator (Above) to back when I had the questions (printed out) and have since lost all of my print outs.

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AWARD: First person to send me all of the questions from webassign (from the serway textbook) will get 3 questions answered by me from each chapter... Pick your hardest questions in each chapter and I'll give you the answer.


  1. Hey Mike I've been having great difficulty with Heisenberg's uncertainty principle. Could you help me out with these two problems, I just can't seem to figure either one of them out.

    1. In the ground state of hydrogen, the uncertainty in the position of the electron is roughly 0.10 nm. If the speed of the electron is approximately the same as the uncertainty in its speed, about how fast is it moving?

    2.The average lifetime of a W boson is about 3.0 10-25 s. Estimate the minimum uncertainty in the energy of a W boson.

    1. Anonymous:

      Off of the top of my head, there are two basic algebraic equations for describing the uncertainty principle:
      1. (delta X) (delta P) (greater than or equal to) = h/(4 pi)
      (See: http://www.relativitycalculator.com/images/Heisenberg_Uncertainty_Principle/uncertainty_proton_position.png )

      2. (Delta E) (Delta t) = (greater than or equal to) h/(4 pi)

    2. So, as long as I'm not misunderstanding anything (and it has been a few years now), you'll set up your equation:
      p = mv
      delta p = m delta v (where delta p and delta v are the uncertainty in momentum and velocity)
      therefore delta v = v (because your question states that the uncertainty in speed is equal to the actual speed).

      And finally you get that delta p = p = mv

      substitute mv in the equation for delta p and get the following:

      v = h / (4 pi deltaX m)
      Thas mass of an electron is about 9.2 X 10^-31 kg
      delta x = 1 X 10^-10 (0.1 nm)

    3. for the second question, use the Uncertainty in Energy multiplied by the uncertainty in time = h/(4 pi)

      Then solve for "E"

      See: http://grephysics.yosunism.com/cgi-bin/mimetex.cgi?%5CDelta%20E%20%5CDelta%20t%20=%20h/4%5Cpi