Well... about the problem of the iron bar:
When you push the bar, you are not pushing the bar as a whole. You are only actually pushing the atoms of it which are in contact with your hand. This atoms will then push their neighbors, their neighbors will push their own neighbors, and so...
The "pushing" that the atoms will do in their neighbor atoms travels trough the entire bar, like a wave, until its end. Look at the picture i did... the first line is the atoms of the bar, and in the second, 3rd, 4th, lines is what happens when you push it. Note that the end of the bar only moves in the last line, when the "pull" of the atoms reach there.
And the speed of this "pull" is not even the speed of the light, but the speed of the sound in that material. In case of iron, it some 3 miles/second.
The fact that the pull goes with the speed of the sound is very reasonable, if you remember that the sound is just the "pull" of the molecules in the air, and the sound actually is just a mechanical pertubation, a mechanical wave, through air, or steel , or whatever.
I hope my explanation is clear enough. If not, feel free to ask! :thumbsup:



EDIT: i cant resist to say that we really dont need to use quantum physics, relativity or strings theory to understand a wave travelling through a bar... its classical physics.