Modulus', Mediums, and Elasticity (Oh my!)

[SKaminski]

---

Members don't see this ad.

So, i know the typical format is one question per thread, but i feel as if all of these are somewhat related, and I don't think each individually deserves its own threads:

The modulus' of young's, shear, and bulk. Do we need to know them for the MCAT?
------------------------
When the word STIFFER is used, do they mean more elastic, or less elastic? What's meant by elastic? Perhaps i dont have a good intuitive idea. Will something that is MORE elastic be MORE likely to keep its shape under strain, and as such be MORE stiff?
----------------------
I read a statement that said "Velocity is dictated by the medium." It went on to say that two aspects affect velocity:

The medium's resistance to change in shape (aka elasticity) and the medium's resistance to change in motion (aka inertia).

What the book never expanded on, is HOW these two variables affect velocity? Does it decrease them or increase them?

Thanks!

 

[FormerPhysicist]

Young's modulus is the only one that might need to be memorized (although the likelihood of seeing it is pretty small). Bulk and shear are a little bit outside the scope of most pre-med classes and will probably be given if they're needed in a passage. That said, it doesn't hurt to understand how they work.

Elasticity (as I understand it) refers to the amount of energy needed to change the shape of an object. Example: rubber bands show more elasticity than a similarly-sized band of steel. The steel band would be stiffer, therefore less elastic. The higher the elasticity, the more the shape will change with strain.

As for the last part, it appears to be referring to the variables that account for viscosity of a medium. I'm less familiar with fluid mechanics, but I would assume that higher inertia at least would heighten viscosity. As for the elasticity part, I'm not quite sure.