Quote (BiGDaviDx1st @ Sun, Jan 25 2009, 10:19pm)
go ice skating, then go really really fast, then stop all of a sudden and fall.. but slide a couple feet.
thats not the best way to describe it but thats newton's law of inertia in a very simple way.
A good example I can think of is in outer space. Imagine you are outside working on the space station. If someone pushes you, and there is nothing hold you on to the space station, you will keep moving until you hit something, or are acted on by another force.
You have to remember that this only occurs with *no* forces acting on an object, after the initial force (i.e. the push in the above example). For example, if you push something across a table, the friction will eventually make it come to a standstill.
I imagine even air will slow something down. However, by the time this happens, the object has already hit the ground due to gravity (think of the arc that occurs when you throw something). As a result of friction and gravity, it is rare to see this law in action on earth. An ice rink or air hockey table is about as close as you will get in an everyday situation (unless I'm missing something obvious), however, even they are not perfect (since even when you hit an air hockey puck, you will notice it still slows down eventually).
Obviously this is far from proof, but the law *does* work and has worked for us so far. Maybe there are situations we haven't thought of where it won't work. It is impossible to conclusively exhaust all possibilities though. It's a bit like a large computer program in that it is impossible to prove that there are *no* bugs whatsoever.