What are your favourite classical physics puzzles?

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Discussion Overview

The thread invites participants to share their favorite classical physics puzzles, encouraging a variety of problems that can be engaging and thought-provoking. The scope includes theoretical challenges, conceptual inquiries, and mathematical reasoning, with an emphasis on elegant or creative solutions.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant presents a problem involving three co-planar point masses and their gravitational interactions, asking for the angular speed of rotation and relationships between distances.
  • Another participant poses a question about the shape of an asteroid with uniform density that maximizes gravitational force at a point on its surface, comparing it to a sphere of the same mass and density.
  • A participant introduces a problem involving a ball rolling along a curve defined by its curvature, seeking to find the curvature and torsion of the resulting path on the ball.
  • Several participants express curiosity about the increase of entropy, with discussions referencing classical statistical mechanics and the Boltzmann H theorem.
  • There are multiple inquiries regarding the intuitive understanding of rolling without slipping and the implications of molecular chaos in kinetic theory.
  • Some participants challenge the assumptions underlying the H theorem and the relationship between the causal and thermodynamic arrows of time.

Areas of Agreement / Disagreement

Participants express a range of views on the puzzles presented, with some engaging in deeper discussions about entropy and kinetic theory. There is no clear consensus on the interpretations of the H theorem or the implications of molecular chaos, indicating ongoing debate and exploration of these concepts.

Contextual Notes

Discussions about the assumptions underlying various theories, such as the molecular chaos assumption and its implications for the arrow of time, remain unresolved. Participants highlight the complexity of these concepts without reaching definitive conclusions.

  • #31
@wrobel I missed the part ##\omega## is parallel to the plane.
 
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  • #32
etotheipi said:
wondered if people would like to share some fun problems that you can snuggle up to on a cold Winter's evening?

There is a sailing race down a river which flows at 10 km/h.

- On the first day the wind relative to the ground blows at 10 km/h parallel to the river in the downstream direction.

- On the second day there is no wind relative to the ground.

During which day can the sailboats make faster progress down the river?
 
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  • #33
I believe the correct answer for @A.T. 's sailing puzzle is the second day.
(I've done a little sailing, and to head into the direction the wind is coming from, you zigzag toward the destination).
 
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