MadSci Network: Physics |
Clif,
The equations for spring force (F = kx) and elastic potential energy (PE = .5kx^2) are what we call models. They are an attempt to explain observed behavior and are used to predict future behavior. And ideally, for a perfect spring, k would be constant. But, in the real world, it's difficult to make a "perfect" spring. With a good spring, in it's normal range of use, k will be fairly constant. But if you measure very accurately, you'll find that k may vary slightly for all sorts of reasons. These reasons could include manufacturing defects, inconsistencies in material, or other reasons. Also, springs can be made to follow a different equation such as F = kx^2. They may also be manufactured make a sudden change in spring constant at some point during their range. With almost any spring, it will definitely start to behave differently if you stretch it too far. At this point it begins "plastic deformation" instead or "elastic deformation." Once this happens k will no longer be constant and it won't spring back anymore. Hope that helps you.
Your Mad Scientist,
Mike Scannell
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