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- Thread starter rons49
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- #2

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What is hookes law? Are there limitations of hookes law?

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F is the force applied to the spring in newtons (N)

k is the spring constant measured in newtons per meter (N/m)

x is the distance the spring is stretched from its equilibrium position in meters (m)

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σ = Eε

My teacher told us that this (^) was hooke's law. A quick look on wikipedia shows F=-kx, but also I can find σ = Eε if I scroll down a bit.

I know that sigma is the stress caused on a certain area (like the area of the cable holding up an elevator), E is the elastic modulus of a certain material, and epsilon, umm I don't know the word for it in english but I know what it is. :)

Thanks in advance.

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F = -kx is an equation of motion. Your σ = Eε seems to be more of a definition of materials.

- #8

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σ = Eε

My teacher told us that this (^) was hooke's law. A quick look on wikipedia shows F=-kx, but also I can find σ = Eε if I scroll down a bit.

I know that sigma is the stress caused on a certain area (like the area of the cable holding up an elevator), E is the elastic modulus of a certain material, and epsilon, umm I don't know the word for it in english but I know what it is. :)

Thanks in advance.

The σ=Eε is the general Hooke's law. It may be applied to any piece of elastic material, of any shape. In general all terms are tensors. For the simple case of a bar pulled by the ends with a force F , σ is the force per unit cross section area and ε is the relative elongation.

E is a material constant (Young's modulus).

F=-kx applies to a spring or any elastic object. Here k is a constant of the object and not of just the material. Springs made from the same material may have different values of k, depending on size and shape.

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