S2 – Days 6-8 – Beginnings of Energy

Well apparently I can’t keep up the blog daily…  so here is where we are!  We finished up momentum and did the test.  It was mostly good, except for some kids who are really struggling…  but then, they are not coming for help, so…. what can you do?

We began the energy unit with an abbreviated version of the stations we do each year – we wanted to focus more on Ek, Eg and Ee and get rid of some of the other stuff.  I think this worked out great!  We also spent some time in this class reviewing for the momentum test.

Next, we did the energy skate park phet sim.  In the past, we had a version of this that was a hold over from before I was involved  in freshman physics, and every year it seems needlessly lengthy and complicated.  So @MissMLMedrano and I decided to just let them play with the sim, and then whiteboard some claims and evidence and see where it went.  This was an excellent call!!!  They did super well with this!  We had them focus on the total energy staying constant, and the thermal energy growing and never transferring back to another column.

Next up:  BIG developing energy equations lab!



S2 – Day 5 – More practice and car crashes

Today we just did a little whiteboarding of practice 3…  I did it a little differently in each class.  By the end, I had them pairing up to re-do one on a whiteboard that they had missed.  Afterward, we had a discussion about WHY people missed certain problems.  It was almost always messing up the sign of the velocity (despite going over this 1,000,000 times…   I haven’t yet cracked how to fix this one)… the other was they kept messing up the change column (final-initial)….  not sure what to do about that either.  This is the first try using the momentum tables, so we will see if I come up with anything… overall though, I am pleased with how they are doing, and that they are being forced to work on their algebra skills!  I gave one more practice for HW and that’s it.

Next we discussed car crash safety…  I have two videos that I like to show, and we stop and talk about them.  I really like this day because I am able to give them some practical tips on staying safe in the case of an accident.

New vs Old car crash

Staying safe in a crash

Lastly, we went over the impulse equation, as derived from N2L.  We will not do quantitative impulse problems due to time (though I did make an optional challenge set and a couple of kids took them).  We will only use proportional reasoning here, since we really care about the force-time relationship…  forgot many pics today, so I will just use one of a whiteboard and the packet!


S2 – Day 4 – Practice and Eggs

Today we continued some practice with the new momentum tables to solve collision problems.  I’m so glad we persevered through the difficulties last class, because it is getting much smoother now!  I started by doing one more example for them, then @MissMLMedrano found some funny youtube videos of crazy kids running into each other with bouncy balls and bubble wrap – so we created a problem around that and had them whiteboard it.  I really like having them all work on the same problem on big board all around the room, so I can check and see how they are doing.  They did fairly well, mainly issues with signs – missing negative velocities and also subtracting a negative makes a positive.

I am SO GLAD we are doing this, because I think they really need this algebra practice.  Also I was thinking, that sometimes maybe this might not look “rigorous”, but these kids are doing a ton of thinking…  such as how to scaled the graph, trying to find commonalities in numbers to divide up the mass boxes, etc…..

We also wanted to do a little intro to impulse – we usually do a water balloon toss, but it has been raining!  So we did a little egg drop for about 30 minutes (taken from https://classroom.iihs.org/), which was super fun!  We will use that to springboard into the discussion of force and time next class.


S2 – Day 3 – Momentum Charts

Today we dove in to the math of collisions and conservation of momentum….  it has been a few years since I have taught this, but I remembered it being very tough to do an m1v1i+m2v2i=m1v1f+m2v2f….  so many letters, subscripts…  the kids really struggled.  So this year I went to twitter to get advice on using some kind of chart – we have used charts and templates with many topics and the kids do well with them.  I remembered seeing it on @fnoschese ‘s blog…  got some advice on twitter from him and some other helpful folks!  THANK YOU!

So anyway, I worked over the break to tweak it a little, and finally figured it out.  Today we did it in class, I started with one using the physics classroom sim that had all of the numbers, then went to ones with variables (mainly unknown final velocity).  My block 4 was first, and they are usually pretty quick at it, but they were somewhat confused…. my amazing colleague @MissMLMedrano had similar issues…so we had a quick brainstorming session during lunch to prep for the next two classes!

We decided to do the boxes in a certain order, filling in the 4 momentum (p=mv) ones.  Then add the first two columns down to total.  Then do first two rows, change across.  Then set up two equations with the last row and last column, solve, and you should get the same answer.  This structure worked much better!  I also had my kids leave out the units, since that makes it super confusing for them, and my real goal in setting up these equations is to practice algebra, which many of them need desperately.

I think this will go well once they practice a bit, despite the rough start!  Some of the first ones we did were very easy and kind of intuitive – so my faster kids were resisting doing all of the required steps…  I do really hate when kids don’t listen when I am trying to help them prepare for harder problems later….

Either way, they seemed to be getting the hang of it, we will see next class!


S2 – Day 2 – Conservation of Momentum

Today was one of my favorite days, since this intro-slide meme is my favorite of the year!! 

We whiteboarded Practice 1, to be sure everyone was ok with basic momentum calculations, and all of the new representations.  Algebra is still a struggle for many of these kids, so we are looking for more ways to incorporate simple skills into what we do.

The whole momentum packet is here:  Momentum Packet


Next, we did a discussion intro-ing collisions and conservation of momentum, taken years ago from @fnoschese here and here.  This went really well!  We learned how to draw velocity vs. mass graphs and see that the momentum is conserved.

We had only a few minutes left, and we looked at the sim from physicsclassroom.com  that you can find here.  Only one class got to trying out the new momentum table…  the other classes will just focus on drawing the sketches and graphs – we will tackle the math next class.

I think I have quite a few kids who are going to blow easily through these collision problems, so this weekend I am going to put together a mini-packet on quantitative impulse (otherwise we are just doing it sort of qualitatively to save time)….  it will give me a chance to finally try out a new problem solving template I have been playing around with for a couple of years….


S1 – Day 1 – Momentum Intro

Well things got hectic and I fell of the blog train…  ugh.  This semester if I get behind I just need to pick back up where I am at instead of trying to catch up…

Fall went pretty well, we spent a bit more time on forces and I think they did well overall.  We wanted to get a bit of momentum in this year, so we are going to spend a bit of time on it…

Today we did the momentum invention task from Rutgers and it was amazing!  I got the momentum one  – I believe we got the password when we went to the AAPT summer camp – website here:  http://depts.washington.edu/pits/

The kids did a good job finding the “danger index” of the pac-man, though they were a little frustrated at first, which is a good thing!  Then I set up a sheet for them to compare battles, focusing first on either speed or strength, then later as the combo (AKA momentum). I was impressed with their thinking!

This went really well!  We whiteboarded the battles, defined momentum, and learned how to use the new template including proportional reasoning and velocity vs. mass graphs.  We are focusing now on just one object’s momentum, next class we will start collisions.




Day 26 – Wow, forces are difficult!

Today we tried a little something different….  the past two years the kids have REALLY struggled drawing force diagrams.  There are so many problems…  So this year we decided to break it down a bit.

We started with only one object, I drew an example last class of a book on a table, we did the force diagram of the book.  Today we did three more scenarios – mass hanging from spring scale, and then same thing, but pulling down or pushing up a little on the mass.  I am also trying to call it “cylinder” since calling it a “mass” always seems to cause issues.

I drew the interaction diagram and force diagram with them for the hanging cylinder.  I told them when they read the spring scale, it is telling them how hard the spring scale is pulling (Ft).  Then I let them go.  One class did great, one ok, and one (as expected) struggled a lot.

They first had to figure out that the spring scale reading equals the Fg since the cylinder is not moving, and the forces must be balanced.  Then, for the next two, most classes at least drew three forces, though the had lots of ideas about how to draw them… this was new, I usually just show this, but I let them struggle with it for awhile.  Also they didn’t have much idea what to do with the numbers, so there was all kinds of variety there…  I tool many pictures of their (incorrect) boards.  In the struggling class, many groups didn’t even draw three forces, often left off the Fg…  we have a lot of work to do.

We circled up for a board meeting, and I walked around and pointed things out, starting with the Ft=Fg for the first one.  Then we talked about the Fg interaction between the cylinder and earth…  and decided nothing about THAT interaction changed (the fact that my hand was now there on the other two doesn’t involve the cylinder-earth interaction) – so the Fg should stay the same across all pictures.  Then they started to figure out how to balance the forces.  We also had a discussion about whether to put arrows side by side, or to stack them, and decided stacking them made it easier to see if they were balanced or unbalanced.

After this, we went back to the book-table diagram from yesterday and now looked from the table’s perspective.  We drew the force diagram for the table, and then identified the  N3L pair…  must be the same force type, same feeler-dealer,but swapped positions.

Lastly, we did an example (originally taken from @fnoschese I think)…  and made it quantitative.  Wow this is hard.  Really really hard.  A couple of kids came after school and I remembered all of the problems…  they don’t always mark the weight as Fg, they mess up the force types…. the have trouble identifying what is happening.  Well, it is the hardest unit of the year, I have been warning them.  We will press on and hopefully the way we are breaking it into smaller pieces will help them.

Overall, I really liked the new sort-of-exploration way to move forward with force diagrams!  We will see if it pays off…  time will tell!