There are few contests that go on for very long. Generally speaking, if a winner isn't clearly established within a few decades, the contestants get bored and decide to go for a pizza instead. There is at least one contest, however, that seems like it could last forever. That may be because the contestants aren't mortal. They're not even immortal. They're mindless properties that seem able to enlist everyone and everything to their respective causes: inertia and momentum.
Inertia, the force that keeps you from doing much of anything, seems to have lots of allies. Momentum, on the other hand, has just one: force. Force is kind of like momentum's conscription squad, pushing soldiers out of the comfortable ranks of inertia and into the struggle behind momentum. Eventually, though, every soldier falls back into the ranks of inertia. This willingness to trade their respective soldiers may well be the primary reason the conflict remains unresolved.
Oddly enough, momentum only seems to need force to get its soldiers started. Once started, momentum alone is enough to keep them going for quite a while, despite inertia's constant propagandist radio broadcasts. We've all experienced the phenomenon: one moment, you're just one more body in the ranks of inertia, then suddenly something happens and you find yourself firmly on the side of momentum. Things seem good for a while. You might even think momentum is winning the battle. Then gradually, you drop back into the ranks of inertia and wonder why you ever left. How does this happen? Is there any end in sight to this constant trading back and forth of us poor soldiers? Probably not. Still, let's consider some examples.
The most obvious example of inertia's power is just how long it's taken me to get another "Pondering" posted to this site. The last one was written almost a month ago! Hoo rah for inertia! Of course, once I started (something like an hour ago), momentum had a strong hold and has yet to let go.
A couple of other examples are more puzzling. I really don't like house cleaning. And yet, something (like a perverse desire to remember what the bottom of the kitchen sink looks like) will cause me to start cleaning something (like the dishes) and before I know it, I'm vacuuming and then scrubbing the toilet! It's like once you're on momentum's team, it has a sneaky way of making you do more than you signed up for!
Yard work is another thing I don't like. But one afternoon a few weeks ago, mowing the lawn didn't seem to be enough to make me desert back to the ranks of inertia like usual. No. For some inexplicable reason, I felt compelled to wander around the planting beds in the front yard and yank up most of the weeds! And I'd specifically told the enlistment officer that I was not doing anything but mow the lawn.
What lessons can be learned from this? Well, for one, inertia never makes you do anything you didn't sign up for. And momentum is a sneaky commander that will trick you into doing all kinds of things you weren't planning on. So, if you're content with nothing (by which I mean everything), then I suggest you hide, lest momentum's conscription team sneak in and haul you off for KP duty. On the other hand, if you're bored with nothing (by which I mean nothing), you either need to work harder to cultivate your imagination, or you might want to call the momentum conscription crew and let them know you might be willing to go AWOL for the right incentive.
For all you physics gurus, please don't bother correcting any inaccuracies in my use of inertia and momentum. I went to , learned just enough for my momentum to fade away, and fell back into the ranks of inertia. So I'm going with my informal, colloquial definitions of inertia and momentum.