2-d equations of motion for a Slinky going down stairs?

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SUMMARY

The discussion focuses on deriving the 2-dimensional equations of motion for a Slinky descending a flight of stairs, emphasizing the planar motion of the Slinky. Key concepts include the force equations ##F=-kx## and ##F=\tfrac{d\vec{p}}{dt}##, which are foundational in understanding the dynamics involved. The center of mass behavior is highlighted, indicating that it remains static during certain phases of motion. Two significant papers are referenced for further exploration: one detailing rigorous treatment of Slinky dynamics and another employing Lagrangian formalism to analyze stair-hopping behavior.

PREREQUISITES
  • Understanding of Newton's laws of motion
  • Familiarity with force equations, specifically ##F=-kx## and ##F=\tfrac{d\vec{p}}{dt}##
  • Knowledge of center of mass concepts
  • Basic grasp of Lagrangian mechanics
NEXT STEPS
  • Read the paper on Slinky dynamics available at arxiv.org
  • Study the Lagrangian formalism as applied to the Slinky in the American Journal of Physics article at aapt.scitation.org
  • Explore the mathematical modeling of cycloidal motion
  • Investigate the effects of boundary conditions on oscillatory systems
USEFUL FOR

Physics students, mechanical engineers, and anyone interested in the dynamics of oscillatory systems, particularly those studying complex motion in constrained environments.

benorin
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This problem fascinated me in lower division physics. Find the 2-d equations of motion for a Slinky going down a flight of stairs (assuming the path of the slinky is planar; eg only going up and down and front and back, no side to side). I do confess that whilst I do love physics I’m not terribly good at it, better with math. It’s been 20 years since physics but I still remember ##F=-kx ## seems a good place to start, or was it ##F=\tfrac{d\vec{p}}{dt}##? We’ll need some initial displacement of the slinky too. I’ll need some clues as to how to proceed... we’re going to wind up with a tweaked cycloid I bet?
 
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benorin said:
we’re going to wind up with a tweaked cycloid I bet?
I certainly would not expect that to be the case. Think about it. The center of mass, which is what you have to be looking for the motion of, is going to be static for noticeable periods while the top of the slinky moves forward and then again briefly as the top catches up on the next step down.
 
Slinkies can actually get super complicated, math-wise.
This paper has the most rigorous treatment that I know of, and includes discussions on the shapes formed by a slinky under various boundary conditions: https://arxiv.org/pdf/1403.6809.pdf

This paper from the American Journal of physics uses a simplified model of the slinky and a Lagrangian formalism to look at its stair-hopping behavior: https://aapt.scitation.org/doi/full/10.1119/1.3225921
 
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