Let's say you and your friends are hanging around, bored on the weekend with nothing to do, when you happen upon a giant tire. Better yet, the tire is at the top of a huge hill with a lake at the bottom of it.
You're not just gonna leave that thing there. No way! You're gonna push it upright, force it over the curb, and set that thing free.
Cause believe us, once gravity gets a hold of it, things turn pretty awesome pretty quickly.
Let's just hope there weren't any swimmers nearby.