Molecular model of force and conduction

E2 is trying to figure out a relationship between energy and forces. One of the claims on the table is something like, "An energy transfer is always caused by a force." My physics-self's first response is no, that is not true; there is conduction and radiation and so on, those are energy transfers not caused by forces. (My physics self is sometimes a bit smug at first.) But then Jessica said this:

"If this is sitting on a table, there are a pair of forces, the eraser down on the table the table up on the eraser, and the claim that this group had earlier was that there's a force here, a pair of forces here, but there's no energy transfer that results in movement. So we started to talk about how there is an energy transfer that is in equilibrium, and it's heat transfer, so then we talked about our difficulty around the word movement, which is too wishy-washy of a word for us to get behind as part of a definition. There's no net gain or loss of energy but there's energy transfer happening at all times between any two objects that are in contact. And when you're talking about radiant energy or magnetic energy they don't need to be in contact."

Again, I have an initial response (that I am a little embarrassed by) of saying to myself, "Well, she's mixing up conduction with contact forces; those are totally different." But on what basis do I say that? She is modeling both conduction and contact forces in terms of molecular interactions. I do that too, and yet I have this idea that the two are completely separable. I don't think that's any kind of obvious reality; I think that's just how I've been raised. On further reflection, I'm thinking that my model of contact forces is that the molecules are little springs, and to push harder on a solid object compresses the little springs further; whereas my model of warmth is that the molecules are little ping-pong balls zooming around, and when something gets warmer the ping-pong balls zoom around faster (on average). These are separable ideas. But I am still challenged to explain why something that is warmer doesn't feel heavier. Wouldn't the ping-pong balls hit your hand harder when they go faster, making it feel like the eraser pushed harder on your hand?

I think I can resolve all of these physics questions for myself. But I hope I am conveying something of what I love about working with teachers, which is that they ask me physics questions that physics culture has trained me not to ask myself. Here's another post on this topic.