Physics DB V

DB V

• Your initial post should be at least 200 words in length.

As we have learned in this unit, Hooke’s law cannot perfectly predict the relationship between stress and strain of materials. See Figure 10.33 in Section 10.8 of Chapter 10 in the eTextbook. Can you provide your opinion why the materials behave like this on the elastic limit? Do you think we need new physics to explain that? Share your idea with other students. 

Response 1: Allison Burch

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Hooke’s Law states that stress and strain are proportional within the elastic limit, meaning a material should return to its original shape when the force is removed. However, in real life, materials don’t always follow this perfectly, especially as they approach the elastic limit. After looking at this concept, I think the main reason materials behave this way is because real materials are not perfectly uniform at the microscopic level. At small levels of stress, atoms in a material stretch like tiny springs, which is why Hooke’s Law works well at first. But as the force increases, the internal structure of the material starts to change. Bonds between atoms begin to stretch unevenly, and some internal defects (like dislocations or imperfections) start to move. This causes the material to gradually stop behaving in a perfectly linear way before it actually reaches its breaking point. That’s why the stress-strain curve starts to curve instead of staying a straight line. I don’t think we need completely new physics to explain this behavior. Instead, it seems more like an extension of what we already know. Classical mechanics and materials science already account for things like plastic deformation, molecular bonding, and material imperfections. So rather than new physics, it feels more like more detailed modeling of what’s already happening at the microscopic level. Overall, Hooke’s Law is still very useful, but it works best as an approximation for small deformations, not for real-world materials under higher stress conditions.

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Response 2: Bailey Phillips

Hooke’s law is kind of like a “good approximation” for how materials behave, but only at the beginning. When you first stretch or compress something, the atoms inside are just slightly moving from their normal positions. I would compare this to like tiny springs. In that range, everything is neat and predictable. The stress and strain have a straight-line relationship. But once you push the material too fast, past the elastic limit, things get messy. This kind of makes me think of what happens between students and teachers. Teachers are always nice and easy going, until the moment that they are pushed too far. The atoms aren’t just stretching anymore; they start slipping past each other or breaking their original arrangement. I have spent a lot think about this and I have been picturing it like pulling on a paperclip. At first, it springs back, but if you bend it too much, it stays bent. That’s because its internal structure has permanently changed. It’s going through complex changes inside, like bonds rearranging.

I don’t think we need new physics to explain this. The physics we already know, like atomic forces and material structure, can explain it. Hooke’s law is just a simplified model, and real materials are more complicated than that. It gives us a nice example and jumping off point, but we have the physics to get it done.