Context: This clip is from small group discussion during Book Club on the Energy Theater paper. This group (Mary, Sid, Bryan, and Wendy) were talking about how doing Energy Theater has made them aware of the challenge of reconciling micro and macro views of scenarios, which leads them back into discussing the piston scenario from that morning, which Mary has been pondering over lunch. The group discusses whether the word "elastic" could be used to describe the scenario, and discuss several examples of "differentials" in energy scenarios.
Interesting Features:
--Mary shows some anxiety about being "off-topic", saying, "I was thinking about this...well I guess I'm not talking about the article..." and later, "But remember the hand-held...is it ok that's we're ignoring..."(gesturing to the paper), I mean..." (she throws a conspiratorial look at Sid)..."the handheld flashlight..." Wendy reassures her, "We're not! We said, it's the micro/macro where we get messed up, and that we see that, and now we're exploring that."
-Some group members seem to be thinking of elastic as meaning a differential of any kind, because a differential produces a "spring-like" effect:
Sid: And so the reason why this works is the differential in pressure?
Wendy: Is that elastic energy then? I don't know.
Bryan: (with certainty) Yes.
Wendy: You think?
Bryan: Sure!...It's spring-like.
Wendy: It is, I mean I think it is
Bryan: It's returning...
Wendy: To a natural state
Bryan: To its original...to its equilibrium
-Other group members give examples that contradict this idea:
Mary: The handheld flashlight, the reason it worked was the temperature differential, but we didn't say there was an elastic energy there.
Sid: Cause there was no physical compression going on.
Wendy: There was no distortion.
Bryan: So there was no kinetic in the flashlight, is what you're saying, it was all thermal. Does that make sense?
...
Wendy: And you know, I don't think it is elastic, because when you suck on a straw, the reason the liquid comes up is the pressure differential, and they don't call that elastic.
-The group generates some alternative piston scenarios to help them try to understand how it works:
Mary: If you somehow made the room's pressure match this pressure...I'm ignoring this (points to article)...it wouldn't do anything
Mary: What if you had the piston not compressed, but the machine could somehow still move its handle? I don't know how that would be. But then you took the room outside of it, and took air out of it, so you lowered its pressure.
Bryan: It would work.
Mary: So you didn't actually compress this.
Bryan: You did the opposite.
And Sid's question at the beginning ("so the reason why this works is the differential in pressure?") is satisfyingly mirrored by Bryan's conclusion at the end ("There's gotta be a difference.")
Transcript
Mary: I was thinking about this...well I guess I'm not talking about the article...
If you somehow made the room's pressure match this pressure...I'm ignoring this (points to article)...it wouldn't do anything
It's something to do with the pressure difference between outside and inside
Sid: And so the reason why this works is the differential in pressure?
Wendy: Is that elastic energy then? I don't know.
Bryan: (with certainty) Yes.
Wendy: You think?
Bryan: Sure!...It's spring-like.
Wendy: It is, I mean I think it is
Bryan: It's returning...
Wendy: To a natural state
Bryan: To its original...to its equilibrium
Mary: But remember the hand-held...is it ok that's we're ignoring (the paper), I mean...(conspiratorial look) the handheld flashlight!
Wendy: We're not! We said, it's the micro/macro where we get messed up, and that we see that, and now we're exploring that.
Mary: The handheld flashlight, the reason it worked was the temperature differential, but we didn't say there was an elastic energy there.
Sid: Cause there was no physical compression going on.
Wendy: There was no distortion.
Bryan: So there was no kinetic in the flashlight, is what you're saying, it was all thermal. Does that make sense?
Mary: What if you had the piston not compressed, but the machine could somehow still move its handle? I don't know how that would be. But then you took the room outside of it, and took air out of it, so you lowered its pressure.
Bryan: It would work.
Mary: So you didn't actually compress this.
Bryan: You did the opposite. (Bryan talks about pistons in a car for a while)
Mary: So if the air was a lower pressure than the piston, the handle would get pushed in?...I mean if the air was higher pressure...
Sid: (Draws a picture) If I had low pressure here, and high pressure here, it would go in.
Bryan: There's gotta be a difference.
Wendy: And you know, I don't think it is elastic, because when you suck on a straw, the reason the liquid comes up is the pressure differential, and they don't call that elastic.
Mary: I think it just comes down to, you're increasing this contact between objects, this concentration of...
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