Recent content by John1951

  1. J

    Feynman's (err, Gottlieb's) infinite pulley problem

    Thanks very much for all the help on this. It led to a lot of thought and finally to understanding of this problem.
  2. J

    Feynman's (err, Gottlieb's) infinite pulley problem

    Homework Statement OK, I've worked up my nerve to ask a stupid question about this problem. I've read the various discussions of it, but I'm clearly missing something.2. Homework Equations [/B] The right-hand mass is 1/(1-t). The sum of the left-hand masses (an infinite series) is also...
  3. J

    Why Does Virtual Work Seem Incorrect in This Statics Problem?

    You are quite right and now I see your point! Since the weight is at the end of a thread, as the inclined plane shifts horizontally beneath it, the weight moves not vertically, but normal to the slope of the plane (tangent to the circle described by the weight moving at the end of the thread)...
  4. J

    Why Does Virtual Work Seem Incorrect in This Statics Problem?

    Thank you. Yes, the cable from W to the wall (parallel to the slope of the inclined plane) remains extended. Since the slope is constant, each Leftward translation x of the plane along its wheels results in W sliding upward and to the right along the plane.
  5. J

    Why Does Virtual Work Seem Incorrect in This Statics Problem?

    Thank you! I'm sure you have answered my question, but I don't quite see it yet. The correct answer (given in the book) is Wsin(theta)cos(theta) Which for theta = 30 degrees gives (sq root of 3)/4. I get this result using the forces method. The problem arises when I use the virtual work...
  6. J

    Why Does Virtual Work Seem Incorrect in This Statics Problem?

    Thank you. I'm not sure I follow, though. Yes, the system is static, but the small shift of the inclined plane leftward and the resultant sliding of the weight rightward and upward along the inclined plane are imaginary (virtual). I don't see how I can imagine that the weight is constrained to...
  7. J

    Why Does Virtual Work Seem Incorrect in This Statics Problem?

    Thanks for you reply. What I equated, though, were two "works": 1). The work done by the force (tension) T in (reversibly) moving the inclined plane to the left a small distance x, and 2) the work done by the inclined plane as it moves the weight W vertically a small distance y. The two must...
  8. J

    Why Does Virtual Work Seem Incorrect in This Statics Problem?

    1. The problem statement, all variables and /known data Help! I'm stuck on an exceedingly simple statics problem, number 2.24 in the New Millennium edition of exercises for the Feynman lectures. The problem consists of an inclined plane (inclination angle 30 degrees) on wheels with a...
Back
Top