# Day 128: Back At It

Spring Break in Neenah has come and gone… now it’s the final push to the end of the year.  I always get mixed feelings after spring break.  Panic… sooo much yet to cover (well to learn); Pride– all the students (well most, … no all) have grown so much and are much better (physics) students than they realize; Sadness… this group of students will be moving on, that’s sad (for the most part); Frustration… I still have not figured out how to reach a few students. No matter what I try, it just does not seem to work.

Today was to be the day we had the post – lab discussion for the collisions experiment we started on the Thursday before the spring break.  It seems to be taking longer this year.  I did a few new things this time around.  Each group shot a quick movie of collisions they studied.  Here is an example:

And one more.

I also required the students to use a spreadsheet (or Logger pro with calculated columns) to complete all the calculations. All of the data will be pooled and dumped into one Logger pro file to create a graph of total initial momentum vs. total final momentum.  If the slope turns out to be equal to 1.0, then we know that momentum is conserved.  The new part for me was setting up a google spreadsheet for the (CAPP) students that were required to complete the analysis of a 2D collision using our hover pucks or our air hockey table.  I’m a bit ashamed to admit it, but this is the first time I have used a google spreadsheet with my classes.  It is awesome to sit and watch the data get entered.  Hopefully we will be able to see momentum conserved in both the x and the y directions.  I will probably not go into any detail about the center of mass of a system aspect unless the opportunity presents itself.  In my experience, conserving momentum in two separate directions.

SIDEBAR:  In my mind I am wrestling with my sequence.  I have been teaching momentum( and impulse) AFTER Energy and dynamics.  As of late, though I have read more about teaching momentum (and impulse) BEFORE energy and even before some aspect of dynamics.  I’m just not sure if there is a pedagogical advantage one way or the other.

General Physics:

Today we discussed the Energy bar chart (LOL’s) assessment they took the day before we went on break.  We also had the pre-lab discussion for the Hooke’s Law experiment.  I do not do the traditional Hooke’s Law Experiment with masses being hung on a vertical spring.  I phrase the purpose to include something like this:….  determine the relationship between the force exerted on a spring and the change in length of the spring.  I find it makes it easier for the students to transition to a compression spring because the ‘change in length’ could be a ‘get longer change in length’ (like our extension springs) or a ‘get shorter change in length (like a compression spring that will be used with the Pasco cart launchers). Here is a picture of how the data is gathered:

The spring are pulled horizontally so there is no confusion about any gravitational affects.  This also makes it much easier to transition to the compression spring and determine it’s spring constant.  Each group did two springs to see that the slope of the linear graph does depend on the spring AND to have its data confirmed.

# Day 127: Collisions and LOL’s

Today was all about gathering data for the collisions experiment.  We did not get finished so tomorrow we will wrap up data gathering and the analysis.  It’ll be a chance to have some of the students learn how powerful and useful spreadsheets can be.  I’m also having them post a movie or three of the collisions to our Schoology site so we can reference them during our discussion AND so I can send an email to the parents to let them see what their sons/daughters are up to in physics.  I wish I had remembered to post a Tweet about it earlier today.

General Physics:

Today we WB’ed the Energy Bar Graphs (aka LOL’s).  I really like WB’ing this because it provides a chance for some really rich discussion.  Here is an example:

After we agreed on the analysis for this problem, I made an addition to the problem:

I added a second path and asked from which path, if either, would the crate have a greater velocity when it reached the location marked by the arrow. We discussed it and most agreed it was the same…. but thankfully, some students needed proof.  I used this:

along with a Bee-Spy photogate to prove that the velocity was the same.  Yep, it was a pretty good day.

# Days 125 and 126: Two for the price of one (Wealth and Momentum)

Well, it is two post tonight because I was sick last night… massive head cold tried to take me out… it did not succeed!

### Day 125

The students completed the ‘Forces Diagnostic’ for the second time, the post test.  I have not analyzed the results yet with the awesome spreadsheet, but I did have several (maybe 3) students with perfect scores of 30 (and a bunch with 29’s), none of them had nearly that high on the pre-test.  We also discussed the one problem from the COE test they finished the day before.

General Physics:

So I was NOT FEELING WELL by this time, my Mod 4 class was (in my mind) awful.  I did more telling than asking.  The topic was connecting the Jewels activity to the new topic — energy using the wealth analogy.  I know I mentioned this when writing about the wealth analogy when the advanced class did it, but I LOVE this analogy… so easy for students to identify with.

During my prep hour I decided to swap my approach for the next class.  Rather than TELL the students we are connecting to energy first, then introduce the wealth analogy… I went right from summarizing the ‘data’ from the Jewels to the wealth analogy. I knew this was what I wanted to do, and you know how sometimes a student will say or ask just the right thing at the right time, well it happened here.  The perfect segue.

I asked what it meant if you had earned a lot of jewels and they had been real jewels?  A student replied they would be rich… or wealthy.. bingo, I’m off and running.  During the discussion, the right words and phrasing just came to me.  I wish I had recorded it, everything flowed just perfectly.  The kids were engaged in the discussion… it was awesome.  The last step was to connect it to energy. To get there, I reminded them that our definition of wealth was a quantity that could change one’s life, well getting back to physics, there is a quantity that is capable of causing a change in a system.  The name of that quantity is energy and then we’re off using all the bits from the wealth analogy to build energy concepts.

So even though I felt like absolute shit, the class was really a good one… I went home and went to bed early.

### Day 126

Today was the first day of our momentum unit.  I developed the concept of momentum using an approach I modified from one that Frank Noschese wrote about in his blog post “Inventing Momentum”.  Unfortunately, I could not find the link. The progression using colliding dynamics carts to build the idea of a v-m bar graph, and that the area trapped by the v-m bar is meaningful… we define it as momentum.  He then goes on to explain that momentum is conserved, but challenges the kids to try to come up with a situation (using simulations) to show when it is not conserved… of course they can’t.

I like this progression because it naturally build a pictorial representation for momentum that is especially useful for answering conceptual questions.  I stray from his approach asking the students if they think the trapped areas should be the same.  Sometimes I get lucky and a student will ask,  then I respond by asking how would you test it… now we have a purpose for the collisions experiment.

When we do this experiment, I break the class into four larger groups.  One group will look at six different inelastic collisions (so two smaller groups do 3 each), same thing for elastic collisions, and for explosions.  The last group is my CAPP group, they use our air hockey table (and/or hover pucks) to do 2D collisions.

Tomorrow is about finalizing what the parameters of each collision will be and gathering data.

General Physics:

Today we used our energy blocks to analyze a bunch of situations.  Here is a set of energy blocks:

We use them two ways.  First, I gave them a situation, For example, a basketball held at rest above the ground… what energy asset and how much?  Then move it higher, now how much, then change it to a basketball… or a dynamics cart rolling on a track.

The second way is to give them an initial situation (a spring-loaded Jump-up toy poised to, well jump up) and a final situation (the toy half-way to its maximum height).  The students use two sets to depict the energy distribution.  In a concrete way, they are constructing energy bar charts.

# Day 124: Jewels

The students took the COE problem for the test, and we discussed the first part of the test taken on Friday.

General Physics

We introduced or new unit by playing a game we called Jewels.  The original idea as shared at a Phox Valley Share group meeting many years ago (but I do not recall the original source).  Our only change was from paper Newton bucks  to little plastic jewels.  Essentially, the students play Rock, Paper, Scissors to earn the jewels from each other, all the while tracking the number of jewels using bar graphs.  Here is a snap shot from the action in class:

The students play a number of rounds or R,P, S and track the number of jewels each has and how may the group has.

This activity, and the follow-up questions, combined with the wealth analogy serve as an awesome introduction to energy and energy conservation… hence the name Jewels.

# Days 122 and 123: COE and N2L Tests

For Day 122, we mainly did some conceptual review to finish getting ready for the COE summative test.  I created a series of three clicker questions based on a spring-loaded toy dart gun:

All three questions had the same basic format as the first one:If the spring had been compressed twice as much, the maximum height would be: (A) 1/4     (B) 1/2   (C) the same height   (D) twice as high   (E) four times as high.  After we discussed two more similar problems, I asked the students to ‘quantify’ it by determining the maximum velocity from the values I had given them.

General Physics:

They took the summative test for the unbalanced (N2L) unit.

Then the next day…..

The summative Unit 7 test… broken into two parts, Conceptual and one (power) problem followed by the COE problem the following day.  I find it lowers the stress of the students, especially with a bigger test like this one.

General Physics:

We took the post test for the ‘Forces Diagnostic’ which many of you know by a different name.  I have yet to analyze the results.

# Day 121: The Leaper Lab

Today is usually a favorite day for many of my students. We make Racquetball Leapers (poppers) and use COE to determine several things: the elastic energy stored in the leaper when it is flexed, the effective spring constant, the take off velocity, the acceleration as it takes off from the surface, and the ‘net force’ required to give the leaper that acceleration.  Here is a leaper in action:

Truth be told, the activity is really more about creating a ‘physics’ toy the students get to keep and getting some excellent advertisement for the course.  Some of the values obtained are a bit of a stretch using COE, but in some years, we re-visit the leaper when we get to impulse and  momentum. I made some small mini-force plates of physics (just a small wood platform that attaches to the Vernier Dual Range force sensor) that the leaper can take-off from so we can see the impulse graph.

General Physics:

Today was all about reviewing for the unbalanced (N2L) forces test tomorrow.  I used the results of the formative assessment to place the students in groups. We started with a Ranking Task, this one:

We followed it with some quantitative problem practice.

# Day 120: Two good things today

Today we discussed the COE assessment the students took yesterday. By ‘discussed’, I mean that I went through only the initial set-up– defining a zero, establishing a initial condition and a final condition and writing the COE equation.  After this discussion we finalized the concept of power and developed the mathematical models for it.

Here comes good thing number 1.  I allowed the students some choice work time.  I had three things the students could practice with (more COE problems, W=Ek problems or Power problems). Allowing choice is something I feel the students really like, this was combined with a chance to work some problems in small groups and with me present to ask questions. Thanks to my colleague Shelley for helping me devise this plan.  Speaking of small groups working problems, I wish I knew of a way to foster this more next year.. or maybe it is already happening and I just do not know it.

General Physics:

The plan for today— another formative assessment and more work time on the presentations to be posted on Schoology.  Here comes good thing number 2– after each student completed the assessment, and showed it to me, he/she grabbed a purple pen and logged into Schoology to work through my answer key.  This is an idea borrowed from Frank Noschese, he wrote about it here.  It is awesome idea that gives the student immediate feedback.  I still had them turn the assessment in so I could go through it and I will use the results to put the students into groups tomorrow as we review for the Unbalanced Forces summative test.

# Day 119: Conceptualizing and Quantifying Work(ing)

We started the mod by taking another COE formative assessment.  Here is it:

Unfortunately, most the students did not correctly solve it.  There were two issues: (1) Silly errors (like canceling the 1/2’s) and using 20m as the final height, and (2) More f a conceptual issue, not including any initial kinetic energy, just starting with gravitational.  This surprised me a bit.  Some also went two distinct steps (very top to very bottom, the very bottom to the final height).

After the assessment, we WB’ed a sheet I put together a few years ago to graphically develop the models for work(ing) and power.  To conceptualize ‘when’ working is being done a system, we used the chairs the students sit in. Hold the chair at waist level, is there working being done ON the chair? (No, there is no displacement). Raise the chair up above  your head, now is working being done ON the chair? (Yes, the force is parallel to the displacement).

You get the idea. We also walked with the char at waist level, and pulled the chair across the floor. We used a WDSS as a force sensor to lift a 1.0kg mass above a motion detector (at constant speed) to build graphs of Force vs. displacement so the area trapped is the work(ing).  Then work(ing) as a function of time to build the concept of power (as the slope of the work vs time graph).

General Physics:

Today was strictly a work day. They finished analyzing the data gathered while sledding.  They also worked on creating their presentations that will be uploaded to Schoology in the form of a shared Discussion.

SIDEBAR: Interesting to note that last Friday was the last ‘sleddable’ day… it was nearly 50F here today.

# Day 118: COE WB’ing and Sledding

Today we WB’ed four of the six problems I had assigned last night.  I choose one problem (a pogo stick problem because I have a pogo stick a class several years back all chipped in to get me) and I let them choose 3 of the remaining 5 to complete. I like these days because it gives us a chance to practice some conceptual questions.  For example, one of the problems was a spring launching a mass vertically, I know you all know the problem.  I asked about what effect doubling the spring constant would have on the maximum height… or the ‘take off’ velocity.  I also asked them to predict the shape of a graph of height as a function of compression of the spring.  If I had thought about it earlier, I would have had a Logger Pro graph waiting on the wings.. or better yet a Vpython (or Glowscript) or even Excel spreadsheet with slider bars.  Well, there is always next year!

General Physics:

Today we went sledding.  We used the LabQuest2 (well the x-accelerometer) to measure the acceleration as the students rode down the hill. There are a few things I had not thought about ahead of time.  First of all was the fact that some kids did some spinning, also that it would be measuring the acceleration once the kids were on the horizontal part.  Hopefully the were able to get some meaningful data.  I did not really have a chance to look, I was serving up the Hot Chocolate!

# Day 117: Are you kidding? It’s that easy? and The Sledder Lab

Today we summarized the four main energy models; Eelas, Ek, Eg, and Ediss. After this we finally looked at two COE sample problems.  The first one was this:

It was the same problem I gave the students to introduce the energy unit.  At the time, they solved it (or attempted to) with kinematics and dynamics.  It is about 15 steps to get it done.  I mentioned at the time, we could probably do it in in 2 or 3 steps.  So today was the day to show them that.  They caught on right away… decide your initial and final situations, draw the energy bars so you can write the energy equation, then solve.  For this problem it is Eg (initial) = Ediss (final).  From there I STRONGLY suggested they use substitution… that COE equation boils down to h=μk*Δd.  (There is another step in this, it is to use theΔd and the 70cm rough patch length to find the final resting spot, but that was not thee important part of the lesson.)

In many of the classes I heard comments like the title of the post and that’s actually pretty cool.  One of the reasons I like substitution is that it really helps kids with conceptual questiions like… what happens to the distance is slides if I double the mass?  Well, nothing, mass cancels out.

The second problem was predicting the velocity of a pendulum at the bottom of it’s swing.  This one is equally simple and then we actually check it with a bowling ball pendulum hanging from the ceiling.  We use a Vernier ‘laser-gate’ with one gate timing to check the prediction.  It’s typically very close, but smaller, because there is a tiny bit f energy dissipated.  It provides a chance for us to do this demo:

General Physics:

We discussed the N2L assessment the students took yesterday, then did a fair amount of discussion to get ready for the ‘deployment’ activity.  The assessment was a sledder on a frictionless hill, not realistic at all, because there IS friction.  The goal of the experiment is to determine the coefficient of friction for a sled and the snow.  Yep, we’re going sledding tomorrow.

Through the course of the discussion, we see that we need the angle of the hill,  the combined mass of the sledder and sled, and the acceleration.  To determine the acceleration, we ill be using the LabQuest2 x-accelerometer.  It was absolutely incredible today using the LabQuest Viewer software and our wifi network to show hte students how to set-up and use the LabQuest2.   Way to go Vernier, as always, you guys ROCK.