How Does Ruler Length Affect Spring Constant and Oscillation Frequency?

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Discussion Overview

The discussion revolves around the relationship between the length of a ruler and its spring constant when oscillating, particularly in the context of how these factors influence the natural frequency of the system. Participants explore theoretical aspects, mathematical relationships, and implications for sound pitch during oscillation.

Discussion Character

  • Exploratory
  • Technical explanation
  • Mathematical reasoning

Main Points Raised

  • One participant questions the direct relationship between the ruler's length and the spring constant, suggesting that the spring constant may relate to the curvature of the ruler during oscillation.
  • Another participant presents a mathematical model for deflection in a cantilever beam, proposing that the spring constant can be expressed as k = 3EI / L³, where E is the elastic modulus and I is the second moment about the neutral axis.
  • A third participant introduces the concept of torque, suggesting that it should also be considered in the analysis of the system.
  • Another participant clarifies that the bending moment is more relevant than torque in this context and speculates that changing the length of the ruler affects its natural frequency, which in turn alters the pitch of the sound produced during oscillation.

Areas of Agreement / Disagreement

Participants express differing views on the factors influencing the spring constant and natural frequency, indicating that multiple competing models and interpretations exist within the discussion.

Contextual Notes

Some assumptions about the system's behavior, such as the specific conditions under which the ruler oscillates and the definitions of terms like spring constant and bending moment, remain unresolved.

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When oscillating a ruler with an extended mass on the end, what is the direct relation of the

length against the spring constant of the ruler? I heard the spring constant had some

relation with the curve of the ruler as it oscillates
 
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My take on this:

Deflection at the end of a cantilever beam of length L, elastic modulus E, second moment about neutral axis I, load at end (mass x g) F:

x = FL3 / 3EI

Using Hooke's Law: F = kx

Therefore k = 3EI / L3
 
don't you also have to take into account torque?

T = R x F
 
You're thinking of bending moment (analogous to torque, but preferred when you're talking about beams). The maximum bending moment for the beam that we're considering is the load at the end multiplied by the length: M = FL

However, the OP is talking about oscillating the system. I'm guessing they're wondering about changing the natural frequency of the ruler by changing the length that is free (how far over the edge of thet able it is before you 'twang' it). The change in natural frequency results in a change in the pitch of the sound you hear.
 
Last edited:

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