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>"There are genreally three types of "moduluses" (moduli?) Young's Modulus, bulk modulus and shear modulus.
All three are properties of the material from which the object is made. All three are usually provided in a table in nearly all texbooks. Young's Modulus (Y) is determined by how much object's length will change when subjected to stress.
Bulk modulus (beta) is determined by how the volume of the object will change when subjected to changes in pressure.
Shear modulus is harder to talk about, but easiest to demonstrate: take a thick stack of paper (like a phone book) and with your hand on the top, push horizontally. THe layers of the stack will shear and the top of the stack will move while the bottom stays put. All objects can be thought of as layers of material. HOw easily will these layers separate from each other? THe shear modulus relates how the top layer of a material will move in relation to the bottom layer.
Whenever something is bending , the material is shearing some amount because the inside of the bend gets compressed while the outside of the bend gets stretched. "Layers" of the material have to move laterally to each other."