Forces

[Tetra]

This isn't exactly a homework question, so it might not be in the right thread, but...

 

We've been learning a lot abut forces and such, as well as momentum and impulse.There were two things I was wondering about.

 

1) How do you calculate the amount of foce needed to break something? For example, a board. Do we just use F = ma to find out how much force the board has? And if so, does that mean if we strike the board with that same forcve, or more, then it would break?

 

2) How does force injure a human body? I've never really thought of it before, but the more I think about it, the less I understand. Is it that the bodt is resisting a change in acceleration, and thus it is injured? Or that it's due to force that's just breaking some of the cells or such in the body?

[ydoaPs]

It has to do with the stress on the material.

[Tetra]

So stress (is it the same as pressure) is the amount of force applied over an area, and the strain is the amount of stress an object can withstand?

 

Are there any ways to calculate strain? I've looked around, but it's been referred to "deformation" a lot, though they don't really explain what it is except the basics and some applications.

[Cap'n Refsmmat]

No, stress is related to the internal forces in the object. Check out the Wikipedia on it:

 

http://en.wikipedia.org/wiki/Stress_%28physics%29

[Newbies_Kid]

Stress cause material to deform and that what we call strain. If you apply stress on body, it will elongate or contract and this what we call strain. Stress is pressure (Pa) while strain unit is in (mm). Check out on this url for more information

http://en.wikipedia.org/wiki/Stress%E2%80%93strain_curve