Do you get hot dropping your balls?

In E1 on Monday morning (8/12/13), the class began the day by drawing diagrams for the two scenarios considered the previous Friday: raising a bowling ball at constant velocity and lowering the ball at constant velocity.  The group I am considering in this episode is: Jeff (in blue), John, Sara (in green), and Emma.  In the first half hour of class, they drew the following diagram:

Then they were asked to consider the following two questions: 1) How does the change in chemical energy compare and 2) How does change in thermal energy compare?  What we can note directly from their diagram is that more chemical energy units are initially shown in the lifting case than the lowering case, whereas more thermal energy is generated in the lowering case than the lifting.  What is clear is that they decided on using 8 total units or parcels of energy in both pictures, which may be causing some trouble in their minds.  This episode picks up early on in their conversation, as they wrestle with what their diagram tells them about what is happening.  Jeff, a few moments earlier, says: “We don't end up with as much thermal energy when we lift.  We seem to imply that we don't get as hot lifting something as lowering.”  This leads the group to considering what would happen if they introduced more energy units.  Lane has joined the table and the group is explaining what they have drawn as well as thinking out loud.

This is a tough conversation to follow and I've had to listen a few times.  Jeff begins by suggesting that if they started with more energy units, then more C’s would be left at the end of the raising picture and more T’s would be left at the end of the lowering picture.  Emma chimes in with the idea that if they want to truly represent the inefficiency of human processes (which is something that was suggested earlier in their conversation), then they need to have more C’s transform directly to T’s.  Particularly, it seems that she notices in lowering they show G to T and C to T, whereas in lifting they only show C to T (this can be seen on the diagram).  She says: “we ought to have some parcels of chemical energy converting into thermal energy separate from this [the shown C to T] conversion.”  She notes that by showing more conversions of C to T, then a balance could occur between both pictures, which could lead to equal thermal energy being generated, or maybe even more in the lift.  This is a neat suggestion from her, because it breaks from the mold of every energy unit being fully understood.  It acknowledges that something occurs in the body that we don’t understand but must be accounted for so that our picture makes sense at the end. 

John joins in to describe to Lane the issue that they are having, which is that their picture shows different amounts of thermal energy at the end, but they feel in real life that would not be the case.  He feels bound by the number of “actors” in the diagram.  Again, this appears to be a moment of transition in translating ET to an energy diagram.  He (and his group) started by thinking about a set number of actors, like ET.  They feel confined by this.  Sara adds that the person lifting and lowering the ball should have the same amount of chemical at the beginning of each diagram, since it’s the same person.  Again, a further refinement.  The group is finding ways in which their diagram does not work for them and suggestions solutions. 

Since they are already saying that more energy units would be helpful, Lane bumps them forward with this idea at 1:56, pondering what it would be like if they had an infinite number of actors.  John and Emma continue to express, with more confidence, what the group has been saying these past few minutes.

The final part of the video is really interesting.  It highlights their challenge in resolving their diagram with what they intuitively feel should be true.  At 2:51 Lane asks, “So would you then in the lowering scenario end up with a bigger change in thermal energy?”  John, Emma, and Sara all offer evidence that YES you would end up with more thermal energy when lowering.  Lane, at 3:46, then asks, “Does that seem intuitively right?”  Emma and Jeff both immediately respond NO.  The episode ends here, but two minutes later John adds, “That gravitational energy makes more thermal doesn't make sense to me.  It's just weird.”  This is a fantastic example of cognitive dissonance.  Everyone in the group keeps pointing to their diagram and describing how it shows more thermal energy in the lowering case, yet they keep saying this feels all wrong to them. This swing back and forth happens throughout the 4 minutes, indeed throughout their 45 minute small group discussion.

This dissonance is not resolved in small groups, nor do I think it gets resolved in the whole class discussion, where it comes up again in full strength.  The conversation does go deeper at this point and Lane even brings research evidence to bear.  No general conclusion is reached, but the class appears to agree with moving on.  I hope to pull an episode from the full class discussion as well.

Full episode: E1 130812 0814 T6-1