Elasticity: Feynman's Physics Explained

Feynman Vol II10-11

Elasticity is the way solids deform under stress and spring back when it is released. For small deformations, the strain (fractional change in size) is proportional to the stress (force per area) — Hooke's law. The constants of proportionality, like Young's modulus, measure stiffness. This simple linear rule lets us analyze bending beams, twisting rods, and waves traveling through solids.

The big idea

For small stretches, stretch is simply proportional to force.

Think about it

Why does a spring (or a diving board) push back harder the more you bend it?

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