# Day 42: How to present the solution to this ‘ca’ problem, hmmmm? and a SLO day

As I mentioned yesterday, today the plan was to WB a set of 5 ca problems that the students have had in their possession since last Friday.  There were to be prepared to present the solution either graphically and or kinematically (that is, using the kinematic equations). Rather that me dictating which method I wanted to see, I let the class decide.  Going in to this, I was pretty excited about how I let them decide.  I set up a little Senteo (clicker, or student response system) quiz with 5 questions…. well actually, one question asked 5 times.  Here it is:

Q: I would like to see the solution to Problem #1 presented :    A)  graphically             B) with the kinematic equations.

I ran in anonymous mode to answer the questions, and whichever had the most votes, that was how it was presented.  The results you ask?  In Mod 1, only 1 of the 5 was presented graphically; in Mod 2 all 5 presented with the kinematic equations; and in Mod 3, again all 5 presented with the kinematic equations.  Well, I’m not ashamed to tell you I was a bit surprised.  I was betting that most would want to see them graphical solutions, but I was wrong.  In mod 3, I threw out my hypothesis to the class.  As a teacher, one way to interpret this is so think “Well, they all solved them graphically and are confident in the solutions, but not so sure of the kinematic approach.”  As I said that, I saw a several heads nodding.  What I should have done is ask a follow-up to each question… “I solved Problem #1     A) Graphically      B) using the kinematic equations.   Maybe next time.

General Physics:

This was a SLO day.  If you are reading this in Wisconsin, you most definitely know what a SLO is.  It stands for Student Learning Objective.   In an over simplified way, this is a means to document and quantify student learning.  The SLO (including a whole bunch of components) gets entered on-line.  I do not have an issue with the process.  I have always thought it is  good idea to reflect on one’s practice and to use data to improve it.

SIDEBAR:  I DO wish we had been given inservice time to work through the process as we neared our due date.

So, you might be wondering what we used as our SLO.  We decided to go with the theme of understanding kinematic graphs.  One of the reasons is because this is always tough for students. Another reason is that the timing is right.  We are just getting ready to start our kinematic units with the general kids. A final reason is that it is easily quantified.  We are using the TUG-K (Test of Understanding of Graphs in  Kinematics).  I have read about the TUG-K but have never given it to a class (I have been using the FCI for a long time).  The TUG-K was developed by Robert Beichner at the University of North Carolina. It is very well researched which is another positive.  The version we gave was 20 questions and my class average was 6… so lots of work to do, no surprise there.   I’m looking forward to 5 or 6 weeks down the road when we give the TUG-K again. Not only to see the improvement, but also as a way to evaluate my instruction.  Did what I choose to do help the students grow in their understanding of these graphs?

SIDEBAR:  The way we administered the test was pretty cool and was made possible by Joe Connelly,(you should follow him on Twitter)  a colleague I met through the Phox Valley Physics and Physics Share Group (@PhoxShare).  Joe has put in a huge amount of work so that members of our share group can give a wide variety of concept tests in a secure, password protected online environment.

I’m looking forward to digging into the spreadsheet of results to see exactly where most students are going to struggle. Two days of Parent-Teacher Conferences coming our way tomorrow and Friday, so maybe I will have some time to start digging!

# Day 41: Tom Petty Part 2 with awesome VA.

Today is the type of day I love in physics.  My students knew they were going to be pressed for time today, so yesterday I told them they could get started as soon as they arrived to the physics room.  We have eight minute passing time, and in each of the classes, the majority of the students were already working in their groups before the bell even rang…. LOVE IT!

As promised, here is a picture of the free fall timer.

We even had time at the end of the hour to have a quick post-lab discussion.  We looked at our data (the acceleration value and the mass of the object dropped) and calculated a class average, then compared it to the commonly accepted value.   I then showed the students the video analysis of a lacrosse ball dropped from our electromagnet (it is a few years old) but I was able to get data for the bounce.  Here is a screen capture of it:

Notice the value of the acceleration as the ball travels UP… that’s right ~-9.88m/s/s !!  This definitely surprised a few of the students.  I then related this back to our phan cart that was setup to do a U-turn…. same graphs, then the phan cart when I pushed it up an incline and allowed it to roll back down; this then becomes the steepest possible ramp… just like we discussed in the pre-lab yesterday, but now going ‘up the ramp and down’ rather than just ‘down’.  I love it when I can come full circle with an experiment or concept.

I closed by re-enforcing the idea that all the representations … graphs and kinematic equations apply to free fall, we just know the value of the acceleration.

SIDEBAR:

My class is offered for CAPP credit.  The students taking the course for this credit completed a different experiment.  They used two photogates to gather acceleration data as a function of the angle of the ramp, like Galileo.  The 24 students worked in groups and will pool the data in a google spreadsheet.  They will plot it with Logger Pro, then extrapolate the data to ramp angle of 90 degrees.

Tomorrow we WB the constant acceleration problems, I think I have a pretty cool idea for that, but that will wait until tomorrow’s post.

General Physics:

Today was the last day for our optics unit.  The student took the summative test on mirrors.

# Day 40: The Kinematic Equations, and Tom Petty

We started the class by reviewing the graphs we obtained from the ramp lab and the meaning of the slope for each  linear graph. We also reviewed how to use the golden graph, or the velocity – time graph to solve constant acceleration problems.   I reminded them that the practice sheet they were assigned last week  was due Wednesday and they should be prepared to present the solution to each problem graphically or with the kinematic equations.

“Wait, what?  solved with the kinematic equations…. what kinematic equations?”  Now I have them ! I reminded them that they really had 2 of the three kinematic equations from the EOLS  (Equation Of the Line) for each linear graph we developed in the ramp lab.

The EOL from the v-t graph —> vf =aΔt+vi  —> Traditional Kinematic Equation #1

The EOL from the v^2 – Δx graph —> vf^2=2aΔx + vi^2 —> Traditional Kinematic Equation #2

I refer to the traditional kinematic equation #3 as the “Granddaddy” because it covers all of what we have seen so far. This one is xf=1/2aΔt^2 + viΔt + xi.   To arrive at this one, we go back to the v-t graph once again.  The one I draw has an initial positive velocity and a positive acceleration. I make use of the total area trapped to develop the ‘Grandaddy’.

There has been some debate in some circles lately about only solving problems graphically and not even helping the students develop the kinematic equations.  A large percentage of my advanced students are going to take another physics course in college, and I want them to have seen and worked with the equations they will most likely be given in a single lecture.

We then transitioned into an example of constant acceleration. Once again I went back to our ramp experiment and recreated the stack of graphs we developed.  Then I make the ramp a bit steeper and one more time making it as steep as possible:

The last ramp that is as steep as possible is a vertical ramp.  In each class, one student (thankfully) speaks up and says, “Will the car even roll down the ramp?  Won’t it just fall?”  Thank you very much…. yes, we are going to call it free fall.

SIDEBAR:

I DO NOT call this the acceleration due to gravity… We have not defined ‘gravity’ yet so why would I define an acceleration based on something we know nothing about?

To gather data, I used playing cards to put the students in groups.  Odds gathered data today while the evens worked on the practice sheet, tomorrow we switch places.  I use three freefall timers (picture to come tomorrow) and one group uses our high speed camera to do video analysis.  I hang an electromagnet from the ceiling and attach a bright yellow softball (it has a metal washer taped to it). The electromagnet is turned off and the ball drops.  To help with the data gathering, I also add a light bulb in a socket so the students can see the electromagnet going off and the ball just starting to drop.  Tomorrow I’ll include a video clip with the post.

General Physics

Today was a day that was a bit out of my comfort zone.  We talked about the curved mirror ray diagram assessment they took on Friday and we had three short curved mirror problems to WB.  That only took about 15 minutes total.  For the remaining time, the students made use of the additional study materials we posted on Schoology.  It was another set of curved mirror problems including ray diagrams, and two conceptual reviews.  The solutions were opened up later in the day. I explained to the students that they were in the best position to know exactly which objectives they still needed practice  on.. they were yellow or red on and that there was practice posted to help with each objective.  It was out of my comfort zone because I usually prefer to direct the review a bit more.  For the most part I was pleasantly surprised with how hard most of them worked, and the level of discussion that went on.  We’ll see tomorrow if this plan worked out like we hope it will.

# Day 39: Phinishing the Phan Cart

The first thing we did today was to talk about the Stack-o-graph formative assessment they took on Thursday.  I created it using the the Ramp-n-Rolll applet found here.  Here is what it looks like:

I really like this for formative assessments because of how easy it is to create new situations.  We also finished checking the phan cart predictions.  We used data sharing again and I loved it as much this time as I did yesterday!!

General Physics:

We are nearing the end of our optics unit.  Today the students took a formative assessment on drawing a ray diagram for a converging mirror.  We also WB’ed some mirror problems.

# Day 38: Holy **** Vernier Data Sharing Rocks

As I explained yesterday, we are working our way through an activity with the phan cart.  The two main objectives are to master making the (kinematic) stack-o-graphs for accelerated motion and to learn to solve constant acceleration problems graphically.   Yesterday when I asked the class to graphically determine the acceleration  from one of the phan cart trials, one (maybe two) group(s) of students realized data was needed from the velocity-time graph. They asked me to provide two points so they could calculate the slope.

The next problem I was planning to ask them to solve was to use the velocity-time graph to determine the change in position during the time interval the cart was out of my hand. (I let it go and then caught it a bit later.)

Last night, after I wrote my post,  I decided to play a bit with a LabQuest 2 and motion detector I brought home.   I knew the LQ2 could share data and set up it’s own wifi, but I had never bothered to really try it in class.  As I was reading some help files from the Vernier site, I learned that the new version of Logger Pro (I’m running 3.8.6.2) has a Data Share feature (found under the File menu).  So I decided to give it a try in my classes.

All that I needed to do was to have each group login and open a browser window. I displayed the URL established under the Data Share option on my Smart board, the students enter it and voila… my data shows up on their screen!  (It could also show up on an iPad, or iPhone…)

At first I was a bit bummed that the graphs were not displayed in Logger Pro, even though that was what I was running, the Data Share analysis tools are not as good as the Logger Pro analysis tools.  BUT, then it occurred to me that this was actually a blessing for this activity, because the students actually had to decide what information was needed and grab the important times and velocities from the v-t graph (I told them they could check it using the x-t graph but they still had to show the work from the v-t) …not just use the Integral feature.

Here is what it looks like on the student screen:

and now a close up:

It was so easy to set up and the students really liked having the graphs right in front of them.  I loved that they had to determine what data to gather rather than one group asking for the data and then the others just using it.

I definitely need to play with all these features more.

So yeah, the Data Sharing ROCKS, thanks Vernier! And yeah,   I WANT MORE LABQUEST 2’S.

General Physics:

We WB’ed the mirror experiment and the students now see that the Thin Lens equation is actually he Thin Lens/Mirror Equation.  It was pretty cool to see that they could make use of another experiment from their journal to complete this activity.  Tomorrow we WB a few curved mirror problem.

By the way… DID I TELL YOU THAT VERNIER DATA SHARE ROCKS?

# Day 37: The Phan Cart of Physics and Logger Pro saves the day

Yesterday the students took a formative assessment on kinematic graphs.  I used that to put together some teams that the students worked in as we checked the predictions for the 7 different situations involving the motion of a phan cart (OK… a dynamics cart with a fan assembly). Here are this handout with the situations.Physics Phan Cart Phun.

SIDEBAR:

The fan assembly I use is from Pasco and I have the pulse assembly. This allows  the length of time the fan is on or a delay before it starts to be used.

There are two main objectives for this activity.  The obvious one is to gain more practice thinking about a situation involving accelerated motion and to accurately predict the kinematic graphs.  The second one (and REALLY IMPORTANT) is to use it as an introduction to solving constant acceleration problems using a v-t graph.  This is a truly powerful problem solving approach that I want my students to master.  So, after we check the graphs, I ask an extra question or two… “Use the v-t graph to determine the acceleration”, ” Use the v-t graph to determine the change in position during this time interval”.

General Physics:

We are almost finished with our optics unit.  All we have to determine a mathematical method (equation) that can be used to predict image characteristics.  We saw the types of images formed by converging lenses is the same  converging mirrors, and likewise for diverging lenses and mirrors.

SIDEBAR:

The transition was great for this because one student asked “Does this mean the Thin Lens equation is really the Thin Lens/Mirror Equation?”.  Well, let’s find out.

The plan for today was to use the Thin Lens Applet to gather data for a converging or diverging mirror and test to see if the thin lens equation hold true for mirrors also.  BUT the computers I have would not run the Java so… Logger Pro to the rescue.  I quickly generated six different data sets (object distance and a calculated column for image distance).  Each student worked independently and tomorrow will team up to compare how they made it linear (by trying/making the same modification we did with the thin lens) and whiteboarding.

# Day 36: Another ‘interesting’ schedule

A rather uneventful day today… we had another interesting schedule.  Our Guidance Department organized a College and Career Conference for or students.  There were two main components;  45 minute panel discussion and a Career fair.  There were 25 post secondary institutions represented and even more businesses.  It was an awesome experience for our students, but it meant that I only saw my entire mod 1 class.  For Mod 2, my 8 juniors (of a class of 25) were gone.  For Mod 3 everyone was gone; Mod 4 all seniors were gone, leaving my one junior.  Mod 5 was back to normal.

For mod 1 and 2, we finished WB’ing the WS with the stack-o-graphs and took a practice kinematic graph assessment.  I am using the results of this assessment to put the students in groups for tomorrow.  We will be doing an ILD (Interactive Lecture Demo) with a phan cart.  Nothing with forces yet, just predicting the shapes of the graphs. The groups were according to color; the Red, Yellow, and Green I used to communicate how I feel the student understands/demonstrates mastery of the objective.  S, we have a Green, with a yellow and a red.

General Physics:

Only my mod 5 class met, and they did the same lesson that Mod 4 did yesterday, learning how to draw ray diagrams for curved mirrors.  Tomorrow we (hopefully) move on to quantifying the relationship between object distance and image distance for curved mirrors with an ‘experiment’.

# Day 35: Stack-o-graphs, the sign convention for ‘v’ and ‘a’and Bridging to Curved Mirrors

The plan for today was to WB a WS that had 7 stack-o-graphs.  For the first 5 problems, the given information was a ramp and tower set-up.  Here is an example:

The students created the position, velocity, and acceleration graphs.  I call them ‘stack-o-graphs’ because I like to stack them vertically like this:

For the last two problems, the students are given the velocity-time graph and asked for the other two graphs AND the ramp setup to produce the graphs.

I use this sheet to provide practice for the kids sketching the graphs and to develop the sign convention for velocity and acceleration.  After each problem is presented, and we have answered any additional questions, we add a general statement about what is happening to the object (getting faster or getting slower) and the sign on the velocity (+ or -) and the sign on the acceleration.  It does not take very long for the students to see a pattern:  If the object gets faster, the signs on the velocity and acceleration are the same and if the object slows down they are opposite.  We then extend this to the velocity and acceleration vectors point in the same direction or opposite direction.  I still like to WB this type of practice because during the explanation, one or more students usually say something to the effect that the acceleration is negative because the object slows down (if when they it could, be slowing with a positive acceleration).

SIDEBAR:  I was tempted to play the mistake game that Kelly O’Shea has developed (explained here) but was concerned that  some of the students may not have understood the kinematic stack -o-graphs well enough to realize the mistakes… maybe that is the point though.

General Physics:

As promised, here is the set-up for the two-way mirror demo.

Last week we work with planar mirrors.  Today started our transition to curved mirrors.  I used a bridging activity similar to the one we did with curved refractive surfaces.  Here is what it looks like:

To check the predictions (once the students have discussed it in pairs), we use our Craftsman laser levels magnetically attached to the big WB, with planar mirrors.  This activity does a really nice job of building the concepts a converging mirror and diverging mirror, and showing where the focal point for each is.  Tomorrow we extend it to predicting the image characteristics with ray diagrams, then checking them with the actual mirrors.

# Day 34: I screwed up… twice, and Whoa, that’s Freaky

Well maybe the title of this post grabbed your attention and that’s good.  You should read this and not make this mistake I did, especially since I know better!  By now you might be really curious….

Ok, enough drama building… the way I screwed up is by not listening to what I call “on the fly feedback’.

SIDEBAR:

On the fly feedback is something I hope every teacher does… gauge the class as he/she presents or discusses something.  I guess it could be considered a form of formative assessment.. helping teachers plan and alter a lesson as he/she presents it.

In my mod 1 class (Shorted again to ~48 mins because of the ACT Aspire testing for 9th graders),  the plan was to WB the instantaneous velocity vs.time graph and the (two) instantaneous velocity vs position graphs.  We presented the v-t graphs and that finally defined acceleration for us.  It took a bit longer because the kids were not really giving me any feedback (verbally) about whether or not they fully understood the v-t graph and acceleration.  I know (because of the look on their faces) that some students were confused as how there could be an object that gets faster and have a negative acceleration. (Recall I set it up that way on purpose so we could confront the issue of negative ‘a’ meaning slow down.)  Here lies screw up number one.  I took their lack of response to mean ‘they got it, go on’..   So I did, I went back to the x-t^2 graph to figure out the meaning of the slope.  Our data showed it to be 1/2a.  Again no real response so on I went.  On to the v^2-x graph where the slope is shown to be 2a.  I ended the hour with about a 3 minute introduction to “stack-o-graphs (x-t,v-t, and a-t).  I had an excellent plan based on the success of how I transitioned to velocity graphs from position graphs using video analysis.  I did video analysis of a free wheeling dune buggy going down a ramp and then created a calculated column for the acceleration so I could make an acceleration vs. time graph.  Then I made another one of the buggy going up the ramp.  I had these two files waiting… hardly started the first one with Mod 1.

Enter Mod 2:  I new I need to change a bit for this class.  Again I did not pay attention to my gut.  I thought, well, I’ll just do a better job of explaining the two other graphs, it’ll take less time.  This class is usually more vocal and this day was no different… many questions about negative acceleration and what the (-) means…  A quick glance at the clock… time flying by… not much time….Here is screw up #2.. I kept going?? But guess what…I did not even show any of the video analysis. My intro was way too rushed.  I should have stopped after WB’ing the velocity-time graph, then right to the two VA files.

Enter Mod 3… (At this point, I’m pretty pissed at myself, I know better that this, and I’m usually much better at the ‘on the fly feedback).  So what did I do with mod 3?  I did it the right way!!  I slowed down for the velocity-time graph discussion and did not even try to look at the other graphs/slopes.  It was a natural transition to the stack -o-graphs and my two really nice VA files.  We got through both with a bunch of discussion along the way.  I even thought to do a Quicktime screen recording that I posted for the other two classes as some help for the homework (7  Stack-o-graphs).  Monday WB’ing should be interesting during Mods 1 and 2.

General Physics:

They had three multiple mirror ray diagrams to make.  In my room, there are four long lab benches where the students sit, eight to a bench.  I gave one problem to each table and told them to agree on it, and make sure everyone understood it and could explain it and they had to have a nice picture of it. After about 15 min, I assigned each seat a number (1-8), the rolled my eight sided die twice. This two people had to explain the ray diagram they created using our document camera.  We followed each one by looking at the real set-up.  A set of infinity mirrors, a normal periscope, then a rotated periscope (the top rotated 180 degrees).  We also looked at a corner reflector and a two way mirror demo.  I’ll snap a picture of it tomorrow.  Basically its plexiglass with a spot light on each side.  Sit two kids across from each other, dim one side to superimpose the image (reflection) with the real person on the other side…. “Whoa, that’s freaky!”

# Day 33: Instantaneous Velocity Graphs and Multiple Plane Mirrors

Today WAS to be the day that we officially defined acceleration !! But we did not quite get there. We have slightly shorter classes this week due to our ninth graders going through the ACT Aspire testing.  The plan was to create instantaneous velocity graphs that we could use to define acceleration, figure out what the slope of the x vs. t^2 graph is, and build the general kinematic equations.  We only got the graphs created.

The way we generate the graphs is by a little Logger Pro magic.  Yesterday we defined instantaneous velocity as the slope of a tangent line to a non-linear position- time graph at a instant (clock reading) and a position.  The students use their EOL from the x vs. t^2 graph to have Logger Pro plot a position-time graph that has more data than they gathered, then use the tangent feature (under the Analyze menu). We skip the first and last points, but still have plenty because we generated the times and positions.

From there it is just inserting two graphs.  As you all know, the velocity -time graph will be linear. Based on our set-up, half the class will have a positive slope (and hence acceleration) and the other half will have a negative slope (and acceleration).  It’s aways interesting to watch some students wrestle with a negative acceleration showing the object getting faster.  Truth be told, I always look forward to this.

So, tomorrow we start with the white-board-apalooza.

General Physics:

Yesterday we established the characteristics of images formed by planar mirrors.  Today was the day we learned how to draw ray diagrams to explain (and predict) the images we see.

We stated with the easiest possible case, one object parallel to one mirror:

Here is the ray diagram we arrive at using do=di and knowing that for us to see the image, light from the image must make it into our eye:

Then we progress to the only other possibility; one object NOT parallel to one mirror:

We check both of these with our CD case ‘mirrors’.  The really work well.

The individual practice is to complete a practice sheet with 3 variations of this, including to mirrors parallel to each other, and two periscopes. We’ll also look at a corner reflector and a two-way mirror. The cool thing is we actually have all this equipment so the students will predict the images and then we get to see them for real…. err I mean virtual!