Why Does Hooke's Law Use a Negative Sign in Scalar Form?

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Discussion Overview

The discussion revolves around the use of the negative sign in Hooke's Law when expressed in scalar form, particularly in the context of a block connected to a spring. Participants explore the implications of vector notation versus scalar notation, and how these representations affect the interpretation of forces and displacements in a frictionless system.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants express confusion about why Hooke's Law includes a negative sign when converting from vector to scalar notation, suggesting it complicates the interpretation of displacement as positive.
  • Others argue that the negative sign in Hooke's Law reflects the direction of the spring force opposing the displacement, which is consistent in vector notation.
  • A participant points out that when writing the equations, replacing vectors with their magnitudes can lead to misinterpretations, particularly when equating positive magnitudes with negative components.
  • Some participants emphasize that Hooke's Law is fundamentally a vector equation, and that the signs follow naturally from understanding vector components.
  • One participant mentions that the confusion often arises from not distinguishing between vectors, vector components, and magnitudes, leading to errors in interpretation.
  • A later reply suggests that the formalism used for stress in materials can help clarify the correct application of signs in similar contexts.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the best way to express Hooke's Law in scalar form without confusion. Multiple views on the interpretation of the negative sign and the treatment of vector components remain contested.

Contextual Notes

Limitations in the discussion include potential misunderstandings regarding the treatment of vector notation versus scalar notation, and the implications of these notations on the interpretation of physical laws.

  • #31
kuruman said:
And then there is the recurrent question, "if I substitute numbers for g in the equation, do I use +9.8 m/s2 or -9.8 m/s2 ?"
Years ago I was using a textbook that forced the students to make that choice. In other words, ##g=\pm 9.8 \ \mathrm{m/s^2}##. That was a huge mistake.
 
  • Agree
Likes   Reactions: kuruman

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