So, we started out listing all the possible answers to "What is energy?" -- heat, electric, ATP, the ability to do work, etc. Then we moved into "What is work?" -- landscaping, using force to move something, power, etc. Then Laura wrote out the 1st Rule of Energy: All energy is stored. It must be stored some place and we can "see" something about it. (The "see" is in quotes because sometimes it's microscopic or smaller, beyond our ability to see with our eyes.) For the energy list, we went back thru & wrote down where the energy was stored -- electric in the movement of electrons, solar in the sun & the particles, be they waves or photons, etc -- & separated out the ones that sounded like definitions -- the ability to do work & ability to move. (We didn't do this for work. Would we have come back to it if we had time? This was near the end of the workshop & I know we skipped some things for time's sake.) The things like "heat" & "potential", we put question marks by for later.
Then Laura came up with the Big Questions: Where is energy stored? Where does it come from? Where does it go? (Cotton-eyed Joe...) What does it do? These are the questions we answered in various ways the rest of the unit. (However, a question I am left with is why didn't I get a picture of this board?)
We talked a lot about how energy is only an idea. There's no energy-ometer, you can't really see it. We used 2 specific analogies: Energy is like money & energy is like information. You can store money/ information in lots of ways, you can transfer money/ information in lots of way, they both flow around, but really, they're not real -- They're just ideas. (Yes, even money is just an idea. Really.)
So we first represented the energy in a tumble buggy using a pie chart. We were careful to define what was in the system: buggy, battery, & surroundings. Then we drew the energy pie at 3 different instances: before the buggy is switched on, at the 2-second mark, at the 2-minute mark, & stopped after 2 minutes. These were just qualitative pie charts, the proportions we thought made sense, no numbers involved yet.
& of course we discussed where the energy was stored, where it went, & what it did. I want to get one of those thermal imagers so I can show kids the ghostly "heat footprints" left behind when they walk across the floor. Anyways. We shortened energy stored in the battery's chemical bonds as Echem. (Yet again, sorry there's not subscript capability.) The energy of motion, or kinetic energy, we shortened to Ek. The energy lost to the surroundings we shortened to Elostsurr or Esurr or Elost. (Apparently they used to say dissipated energy that thanks to all the Viagra commercials, Ed now has a different meaning.) Elost is a bit thorny, tho -- Some kids will be literal & think the energy is just gone & lost forever, not simply transferred out of the system to, say, the air molecules as sound/ light or to the carpet fibers as crushing/ heat.
We also drew the same 4 pie charts but only considering the buggy as the system. The pies were much smaller & when it was turned off, there were no pies. (Some groups used dots to show this but we had pies labeled "empty". We figured that a dot would mean something was there & since we didn't change the chemical energy in the plastic, etc we didn't want to show those.)
So then we watched the PhET demo of the energy skate park (which I used last year in Physical Science; https://phet.colorado.edu/en/simulation/energy-skate-park) because that uses pie charts too. (I was glad to hear I wasn't the only one who had trouble with the PhET simulations. My classroom uses Chromebooks & only the HTML5 versions of the simulations work ... & not all simulations have that option. It's annoying because they all work on my home computer -- & my school computer! -- so if I'm not paying attention, I'll choose things my students can't access. Hmph. Anyways.
Don introduced a track with a rubber band strung up at one end & asked us to draw the energy diagram just before release & at a point further down the track. We shortened the energy of the elastic stretch to Eel or (my favorite) Eboing. Then the track was placed on a slant. At the second point, where the cart stops & starts back down, I called that "Sarah's energy", because it went down the hill. But actually we called that gravitational energy (not energy of position, that's too vague) or Eg. & Don did a demo with a popper dropper -- Does the distance it bounces back up change depending what height you drop it from? (& no, it doesn't. They always bounced up to about eye height. Well, eye height on Don.) The energy for the bounce is stored in the shape, not in the falling/ kinetic energy. That'll be fun to do with my kids.
At this point we stopped, did worksheet #1, & practiced facilitating discussions. I'm pretty sure when we get back together in October, what we'll mostly talk about is whiteboarding & discussions. My physics class doesn't start until 2nd tri, so after Thanksgiving, but luckily I'll have Physical Science in the fall. Really, facilitating discussions needs practice, yes, but it'll be so much easier when I'm the person who designed the lesson so I know exactly what I want to the students to discover.
Lab time! We investigated the distance of the stretch length & the pull force -- Each group had a different spring & each group got a different slope. That slope is the spring "konstant", which means we found Hooke's Law: F=kx. But then we looked for energy on the graph -- It wasn't either axis or the line itself (or the slope), it was the area between the line & the horizontal axis. So with a bit of algebraic substitution, we came up with E=(1/2)kx^2.
We also talked about the fundamental units -- meters, kilograms, & seconds -- & derived units -- newtons & joules. A newton is really kg-m/s/s & a joule is really N-m. We also had an aside about Newton & Hooke & their ideas about gravity. I hadn't realized Newton was such a jerk! Which means, of course, now I need to find anecdotes about 180 scientists, one for every school day. :-/
Before we moved on to energy bar graphs, Don did a demo about the different ways we can see energy. He smashed 2 large steelies together & singed a hole in a piece of paper. Does kinetic energy get transformed into heat energy? You bet! It even works with 1" steelies, just not as well.
So, worksheet #3a had LOL charts to fill out. The first L was the initial energy bar graph, the O was the energy flow diagram (what's in the system & what's not), & the last L was the final energy bar graph. Before Don set us loose on this worksheet, he told us a story about Richard Feynman giving 4 blocks to his nephew, & even when the kid lost the blocks, there were still 4 blocks (you just had to find them). So these graphs aren't quantified either, we only used 4 blocks. (This is totally a story I can steal -- I've got nephews...) The tricky part was, if energy was lost to the surroundings -- not one of the 3 choices on the pre-made graph -- we had to draw those blocks with an arrow out in the surroundings. If it's not in the system, it's not on the bar graph.
& then we had our final labs. We investigated the relationship between the energy of the rubber band & the velocity of the cart, between the energy of the rubber band & the vertical height the cart obtained (on a tilted track, obviously), & between the energy of the rubber band & the slide distance (using a friction block). They were trying to stuff things in for our penultimate day -- Normally, for kids, these labs would each be a day or 2.
So, for energy & velocity... Plotting our data on both Excel & Logger Pro, the formulas came up different. Excel: y=1.44x^0.62 & Logger Pro: y=1.35x^0.55. All of the data were the same, so why the difference? Don wrote the equation out as v = __ E^2, did some algebraic rearrangement, & came up with Ek = (1/coefficient^2) v^2, & asked to google "kinetic energy velocity" -- The official formula is Ek = (1/2) m v^2.
For energy & height, during the lab discussion, we drew the 4-block LOL charts. The elastic energy of the rubber band entirely transfers over to the gravitational field energy of the cart of the top of its trip (assuming no friction, of course). We also know that the force of the gravitational field on the cart is F=mg, the mass of the cart times the field strength. My notes are not as clear here but we went from h=__Espring to h=__Egrav to Egrav = h/ coefficient to Egrav = mgh. I'm pretty sure we didn't do a lot of math there, it was using the force (which is mg) vs distance (or h) graph -- Energy is the area between the line & the axis. & google totally verified this.
The discussion of our final lab results had more algebra & less googling. We drew out the LOL charts & showed that all the energy went to the surroundings (thanks, friction!). So we said friction equaled mu times the perpendicular force (or mg). Then we went from d=__Eel to d=__Esurr to Esurr = (1/coefficient) d. We made a force vs distance graph & found the area & came up with Esurr=fd (energy lost to surroundings equals frictional force times distance). Another way to say that is Esurr = (mu) m g d, the work done by friction. We defined work as energy transferred by force with very little discussion & the day was over & we all went home.
We only had 1 reading for this unit, "Making Work Work" (which is the best title ever). Even tho this article was only 12 pages long, it was a harder read than the 44 pages of the 5 Practices book the night before. (sigh) But the whole article boiled down to "work is a technical term & we're misusing it both in speaking & in equations". I really liked his gravitational field & gravitational energy example & the curvature of space-time ... but I needed a graphic for that, not just words. One of my group members suggested How to Teach Relativity to Your Dog (http://www.amazon.com/How-Teach-Relativity-Your-Dog/dp/0465023312), so I have that on order. :-)
Here's another "summation" thing we discussed: When you analyze a graph, what do you look for? 1) slope 2) equation 3) trends in the data 4) values of the data 5) area
Equipment List
Dropper Popper, $3
http://www.teachersource.com/product/dropper-popper/energy
C-Clamps (3 sizes), $11
http://www.amazon.com/TEKTON-91809-Heavy-Duty-C-Clamp-3-Piece/dp/B00BRL59HK/ref=lp_553158_1_3?s=power-hand-tools&ie=UTF8&qid=1436852033&sr=1-3
Big Rubber Bands (24 pack), $3.50
http://www.staples.ca/en/Staples-Economy-Big-Rubber-Bands-Size-117B/product_383318_2-CA_1_20001
Shower Board (4 ft x 8 ft), $13.50
http://www.lowes.com/pd_16605-46498-300_0__?productId=3015239
Expo Markers, assorted colors (12 pack), $16.50
http://www.amazon.com/Expo-Low-Odor-Markers-Chisel-12-Pack/dp/B00006JNK2
Pasco Friction Block, $22
http://www.pasco.com/prodCatalog/ME/ME-9807_friction-block-ids/
Assorted Springs (200), $5
http://www.harborfreight.com/200-piece-assorted-spring-set-67562.html
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