I always say it's great to have friends -- at dinner a few nights ago, I whacked the back of Beck's chair at dinner the other night and she said, "Ouch." I put on my falsely-accused whiny voice and complained, "I whacked your chair, not you." She replied by saying, "Kinetic energy."
Man, is that a great way to sum it up or what? With that one phrase, Becky provided more than several paragraphs of explanation, discussing every aspect of the chair rungs striking her back, from impulse to the physical relationships between velocity and pain. Talk about brilliant! (Though, I still say my hand would have been hurt worse than her back :-)
Thanks, Beck -- I was still thinking about that as I was going to sleep last night :-)