Ball performing small oscillations within a hollow cylinder

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Homework Help Overview

The discussion revolves around a small ball performing oscillations within a hollow cylinder, focusing on the angular frequency of these oscillations under the condition of rolling without slipping. Participants explore concepts related to kinetic and potential energy, the Lagrangian formulation, and the implications of rolling without slipping on the motion of the ball.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants discuss the formulation of kinetic and potential energy, questioning the expression for potential energy under small oscillations and its relation to the angle φ. There are inquiries about the role of the rolling without slipping condition and how it affects the relationship between translational and rotational motion. Some participants also explore the implications of static friction and slipping on the system's behavior.

Discussion Status

The discussion is active, with participants raising questions about the correctness of their assumptions and expressions. There is an ongoing exploration of the relationships between different variables and conditions, such as the implications of rolling without slipping and the nature of potential energy. Some guidance has been offered regarding the understanding of potential energy and the conditions for small oscillations.

Contextual Notes

Participants are navigating the complexities of the problem, including the definitions and relationships between angles, velocities, and energies. There is a mention of a second scenario involving slipping without rolling, indicating a shift in the problem's constraints.

  • #31
I am not sure why only the second term counts/is used. I could make an educated guess, or try to at least. Is it because around the point of stable equilibrium the first derivative is zero as the potential obtains its minimum and the first term is subtracted from the potential to obtain the "effective" potential? Am I close?
The second part of that problem, with the hollow cylinder and the ball, asks for the angular frequency of the small oscillations supposing that this time the ball slips and doesn't roll.
 
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  • #32
peripatein said:
I am not sure why only the second term counts/is used. I could make an educated guess, or try to at least. Is it because around the point of stable equilibrium the first derivative is zero as the potential obtains its minimum and the first term is subtracted from the potential to obtain the "effective" potential? Am I close?

This is not just close, this is exactly it.

The second part of that problem, with the hollow cylinder and the ball, asks for the angular frequency of the small oscillations supposing that this time the ball slips and doesn't roll.

If the problem says "does not roll", then there no kinetic energy due to rolling. Even though I am not sure how one could achieve that in practice.
 
  • #33
It says "slips without rolling". Does that mean that I am solely left with the translational kinetic energy whereas the rotational equals zero, and all my expressions remain the same?
 
  • #34
I believe this is what is meant. But, as I said, I do not like this. Even if there is no friction, a freely moving ball will still rotate inside a cylinder. This is seen from considering the torques due to the weight of the cylinder and due to the normal force. I would bring this up to to your professor.
 

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