Sound as Kinetic Energy

On Tuesday afternoon (8/6/13) in E1, the class activity was to identify all forms of energy that were present in the morning example of a puck being flung across the floor by a bent back meter stick, as well as stating evidence for each type of energy.  At this point in the video, kinetic energy (as in the motion of the puck) and thermal energy had already been identified and categorized.  As the video begins, sound was suggested as a third energy.  Lane begins this episode by asking for evidence.

Emma laughs after posing that our evidence is simply that we hear something.  We’re left to wonder if other people in the class would have carried this line of thinking further or if Lane would have pushed Emma for something more.  Instead, Barbara chimes in with a very interesting point.

Barbara: But that's kinetic energy, though, right?  Sound and uh...I mean, it's a form of kinetic energy.

Lane: A very special kinetic energy. 

Barbara: But it still is a form.

Tracy: But that goes back to the argument that EVERYTHING is kinetic energy. 

Barbara: Exactly.

Emma: So just like earlier we were specific about motion, now we're gonna be specific about sound.

Barbara: So we're gonna say kinetic sound energy, maybe, I mean, wouldn't we?  I don't know, I mean, I would think we would.

{Long silence}

Barbara: I was suggesting to put kinetic in front of sound, since it's a type of kinetic.

After another brief pause, Lane points out that standards suggest there are two broad categories that all types of energy fall under: kinetic and potential.  He goes on to create a third column in their categorization table – the micro story – that will allow for a description of what is occurring at the molecular level.

I’m interested in this episode because sound energy is not one that I hear (pun) discussed often.  And when I do discuss it, I roll it in the broad category of thermal energy.  Yet here, Barbara suggests placing it in the category of kinetic energy.  Then they would have kinetic: motion and kinetic: sound.  Lane bypasses this with the new micro story column.  I’m curious about her characterization of sound as kinetic rather than sound as thermal because it is not incorrect.  It’s just a different way of organizing.

In fact, I’m surprised that earlier in the discussion when thermal energy was first brought up, no one considered the category of kinetic: thermal.  To my thinking, that’s even more obvious than sound as kinetic.  I wonder if that is because of the order the forms were offered.  Thermal was suggested first and heating was the evidence.  Then kinetic was second.  Were these reversed, I wonder if the class might have been prone to bring up the idea that temperature and heating are related to motion of particles.  A little later in the class, Lane asks them to “act out” the molecular motion of each type of energy, so they eventually discuss this.  But it took further prompting to get there.

Full video: E1 130806 1253 T6-1