Newton's experimental law -- Questions about the collision of two spheres

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Discussion Overview

The discussion revolves around a problem from a mechanics exam involving the collision of two spheres with differing masses. Participants explore concepts related to momentum conservation, the coefficient of restitution, and the direction of motion following the collision. The scope includes theoretical reasoning and mathematical analysis related to impact problems.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • Some participants question how to determine the correct signs for momentum equations given the unknown directions of the spheres after the collision.
  • There is a discussion about whether to add or subtract speeds on separation, with uncertainty about the direction of motion.
  • One participant suggests that the direction of motion after the collision is determined by conservation of momentum and energy constraints.
  • Another participant notes that the problem involves a three-body collision, leading to confusion about the role of the surface in the dynamics.
  • Participants debate whether the smaller mass A must reverse direction after the collision, with some arguing that it is necessary for momentum conservation.
  • There is a mathematical consideration that both objects could theoretically pass through each other, but this is rejected on physical grounds.
  • Some participants express uncertainty about the initial momentum calculations, with corrections and clarifications regarding the total momentum of the system.
  • One participant raises a question about using conservation of energy to argue against the larger mass B changing direction.

Areas of Agreement / Disagreement

Participants express multiple competing views regarding the direction of motion after the collision and the implications for momentum conservation. The discussion remains unresolved, with differing interpretations of the problem and its requirements.

Contextual Notes

There are limitations in the discussion regarding the assumptions made about the collision dynamics, the definitions of momentum, and the treatment of energy conservation. The participants do not reach a consensus on the correct approach to the problem.

  • #31
PeroK said:
I just like to figure out what's happening first, if I can, before writing down lots of equations
"Never make a calculation until you know the answer"
John Archibald Wheeler
 
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