Physics & Physical Science Demos, Labs, & Projects for High School Teachers

Archive for the ‘Teaching Techniques’ Category

I’ve been a member of American Association of Physics Teachers for about 6 years now.  If you teach physics, please join!  The journals and posters alone are worth the tax deductable annual dues.  I attended my first AAPT meeting a couple of weeks back.  I learned one or two great new things, met some super people, but I was also a bit disappointed.

Let’s get the negative stuff out of the way.

  • I’m used to NSTA, so maybe my reference is unfair.  AAPT was small, really small for a national conference.  I felt like everybody knew each other because it was the same people every year.  You could get through the entire exhibit areas in about an hour.
  • It also felt like the conference was aimed at college educators.  I know the organizers claim it’s not, but I’m giving my opinion here based on attending one day of a much longer conference.
  • I had hoped that the talk on video in the classroom would give lots of useful tips; how to integrate video, success at flipping the classroom, etc.  Most of the discussion was why video lectures won’t replace colleges.

Now the positives:

  • The first timer special and lunch was a great idea.  Lunch and the company was terrific, I’m glad I went.  The first timer $75 one-day special is a great way to try it out.
  • I got to meet some great people, some new, some who I had previously met online (Kathy, Frank).  Everybody was warm and there to interact and learn from each other.
  • I met local AAPT members who are trying to suck me in to local activities.  I am interest, but they always do them on a Friday night and Saturday.  I may submit, I do need local physics buddies but I love my weekends.
  • Andy Rundquist demonstrated a great use of Jing.  He has his students take a picture of their homework, then narrate the work on video.  The video is their homework submission.  Jing limits them to 5 minutes and when they talk, you can immediately tell if they know what they are talking about.  Andy has them do this for every homework, I’m going to use it sparingly.  Super idea.
  • There is free software out there called Tracker that does video analysis.  One cool use was to take a moving object, like a person jumping into the water, identify several points (hands, feet, head) through each frame, and let the software determine the center of gravity and plot  the motion.  Did I mention free?
  • I really like the sessions where there is a new presenter every 10 minutes.  Lots of great stuff, and if it isn’t, it’s only 10 minutes until the next one.

AAPT was worth my time, I wish I had done the entire week.  It was close enough to home that I was able to take public transportation.  Here’s the problem: if you can get your school to pay for you to travel to one national conference, which do you choose – AAPT or NSTA?

For me, it would be an easy choice.  NSTA has so much more to offer, so many more strands, talks, exhibitors, and people to interact with.  I would love to do both, I don’t see how.  I will get involved locally, AAPT is too good of an organization to ignore, they are worthy of our support.

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This is not a new topic for me, it’s been a burr in my saddle for some time now.  All of the introductory physics textbooks address significant figures in much the same way.  The problem is – nobody in the “real world” uses sig figs.  At the same time, introductory physics isn’t the time to introduce complex error analysis models.

I’m having this discussion with Andy Rundquist of Hamline University.  I asked Andy how they handled this at the college level.  He told me they don’t teach significant figures and pointed me to a very lengthy article discussing why significant figures are all wrong.  The article suggests the use of Monte Carlo analysis its place.  That may make sense on a lab, but not on classwork and homework problems.  The uncertainty article did have a suggestion; use six significant figures for calculations and round the final answer to three sig figs.  The article does a good job explaining the reasoning, and I’m fine with it.  The three extra “guard digits” preserve the accuracy, and the rounding makes the answer more reasonable.

The next step is trying to explain uncertainty and significance of our data.  I came up with an activity I think will work:

  • I will project an archery target on the board.
  • Students will move back about 20 feet and shoot a round of Nerf darts at the target.  They will be far enough back that most of them will shoot a 6, or 7 and not a 9 or 10, at least at first.  Each student will take a turn.
  • We will plot the overall results.  We should get something resembling a normal distribution curve, but I won’t tell them that.
  • I will ask the kids to average the data and come up with a value of x.x +/- y.y and start a discussion on whether or not that represents the data.
  • We will then put a ring or other object on an electronic scale and write the mass with the error in the same way.
  • After some discussion, I will bring up slides of normal, rectangular, triangular, and maybe exponential distribution curves.  I want them to discuss the fit of the models to the data.
  • My goal is that they understand that error is probability.
  • About a week later we will drop rulers and calculate individual reaction times.  This would be a good time to bring back the distribution graphs and perhaps even input our data into a statistical analysis program to find the best fit.

I think this will work and go over well.  I’d love some feedback.  It’s a first pass, what did I miss?

REVISED:

I’m not one to reblog.  Once in a while I get an email asking me to post something.  I usually ignore the request or politely tell them, “No thanks.”

This is from one of those spamish emails I get.  I have searched the site and it links mostly to University of Phoenix.  Regardless, ignore the rest of the site if it bothers you, but the article is worth your time.  It’s called the “25 Female STEM Superheroes of Today”, here is the link: (http://www.onlineuniversities.com/blog/2012/06/25-female-stem-superheroes-today/).”

I know if you asked me to list influential female scientists and engineers, I’d be very hard pressed to name five, let alone twenty-five.  It’s kind of a shame, but it’s nice to know someone is keeping score.

This is me. It’s been a good year.

This has been an incredible year for my students and me.  They continue to give me unsolicited positive feedback over the courses and me as a teacher.  I’m not going to lie, it feels great to know they appreciated me.  The students have seen a direct correlation between their effort and their grade, no more learned helplessness.  Even better, they’ve really learned the material.  I’ve become a better teacher by doing less and letting the students control their outcome.  It’s the kind of story you want to shout from the mountaintops.

So how does a year of SBG wind down?  The AP exam is done, so the students are done, right?  Nope, they are working harder than ever and I’ve become an observer.  Those last few concepts that we started in the fourth quarter were probably the hardest of all.  The kids want those grades to improve.  Every day, they come into class, join up with a classmate or two, meet at the whiteboard and work out problems on whatever concept they want to improve.  This has been going on for over two weeks now and it blows my mind.  The routine has been to stop when there is 15 minutes left in the class.  They erase the boards and I hand out a concept quiz to anyone who wants one.  Everyone is working bell-to-bell and I’m sitting back and watching them help each other master integration.  This is teacher heaven.  As we enter the last week of school, I’ll allow two concept quizzes in a day, not just one.  The quizzes have to be on two different concepts.  Its crunch time and they are feeling it.  I don’t want to pull the rug out from under them now.

First time through using SBG is a hell of a lot of work.  I’d say I got 80% of it right, the other 20% needs tweaking.  Some of my early quizzes were too hard, others were too easy.  I gave some insane quizzes on domain and range.  I’m sticking with WebAssign for Calculus, but I’m giving it up for Physics.  I’ve added a few inquiry labs to my physics routine and I’m hoping to add one or two more next year.  Calculus has been officially approved for the AP label, but honestly, the class isn’t going to be much different.

The biggest difference to me is the connections I have made with these students.  Usually by now I want them gone.  Not these kids.  I don’t think they are really much different from previous years students.  I think the real difference is the way they were mentored through the classes, rather than just lectured to.  I have more students going on to study engineering than in any previous year.  When the pressure of every quiz or test is gone, the classroom becomes more relaxed.  This year we covered more material in every course and had a lot more fun doing it.  Best of all, I have relationships with these kids that are stronger and more lasting.  I’m going to miss them but I’m also going to keep in touch.

I can’t wait to do it all over again in September.

Let me start by saying that I have yet to take a course in teaching through modeling.  I want to, and I will.

I never loved my pulley lab.  I was never pleased with the learning, the kids seem to focus on trying to set up the pulleys and not on what is happening.

Two days ago I handed them this revised instruction sheet:  Pulley Lab Rev D – Discovery Lab.  The instructions are simple, “Your job is to come up with a set of rules that explains what is happening with the pulleys, ropes, and weights.”

Besides the ring stand, support, pulleys, weights, and string, I gave each group a Vernier and force meter.  They set to work trying to figure out what is going on.

After they finished with the first setup, I asked them to tell me what happened.  The weight was the same, so what was the purpose?  Finally one of them said it changed the lifting up to pulling down.  So a single pulley can be used to change directions.  I gave them a few applications, like pulling something up into a tree or the mast of a ship.

Next they started on the other pictures.  They noticed the force changed.  I mentioned that there is a cost to the reduced force, what is the cost?  Their response was less work.  No, work is conserved.  Keep going.

When they got through picture 3, I explained that they were experiencing Mechanical Advantage.  If you hang by one arm, you hold all of your weight.  Add the second arm and you are splitting the weight.  Add a third arm… you get the picture.

As they got through the rest of the diagrams, two challenges remained:  1) what is the cost, and 2) figure out how to rig this up to get a mechanical advantage of 5.  I gave them a hint – picture 2.  They worked for a while without success.  End of the first day.

I came into class and was pleasantly surprised to see all of the groups were already set up and working.  They were twisting the ropes all over the place.  I gave them 15 minutes to play.  They still didn’t understand the cost, so I drew the solution for the MA of 5.  We put a bunch of weights on the pulleys, almost 10 lbs, and I had them all take a turn lifting.  I wanted them to experience the mechanical advantage.  Then we measured how far the weights moved and how much string was pulled to make this happen.

That was all it took, they got it.  In a perfect system, work is conserved.  This led to a discussion of efficiency and how a lever also provides a mechanical advantage.  It was a good day.

Note:  Here is the solution to the challenge at the end of the lab:  MA 5 Solution

Scared, and for good reason

When we did the egg drop challenge a couple of weeks ago, I asked the students to write about their design and the concepts involved in safely landing the egg in their structure.

For them, they had fun and were rewarded for their hard work with no lab report, just a dialog of what they built, why they built it, and the concepts we’ve been studying.  I wanted them to talk about forces, gravity, momentum, impulse, collisions, and any other concept we’ve studied in order to explain the physics behind the effort to save the egg.

I’m thinking the egg got off easy.  I had to read phrases like “depending upon how fast you dropped the egg,” and “the impact of momentum, ” and best (worst) or all, “the egg has many things to be concerned about it not to break”

Other than labs, I haven’t given a writing assignment before and I now think it needs to be a regular event.  Clearly the students can not talk about the concepts.  Although we spend weeks problem solving, discussing, and working in the lab, they can’t put the concept into an intelligent sentence.  How did this happen?  I feel like I’ve failed.

Teachers – how are you handling significant figures?  I’m a bit at odds with my textbook and I’m wondering what the rest of the world is doing.  I’ve discussed my issues with our chemistry teacher, he tends to agree with me, but it’s just the two of us.  Let me explain.

I teach from Holt Physics.  The book treats sig figs mostly okay.  When they provide numbers for problems, they are always precise.  Usually the numbers are in scientific notation, so you know where you stand with your given information.  The book does state that 1500 could be 2 or 3 or 4 significant figures because we don’t know about the two trailing zeroes.  I tell the students to err towards caution in those cases and treat that number as though there are 4 sig figs.  The book correctly states that the answers are rounded to the least significant number of figures.  You all know what I mean.

Here is where we part ways.  I teach my students to carry an extra place while doing calculations.  For example, if I’m dividing 35 by 62, my working answer is 0.565.  If this is my answer to the problem, I would round this to 0.57.  If I’m using this number in another calculation, I would use all three digits.  The textbook rounds this here along the way even when it is used later.  I’ve even seen problems where they have rounded more than once in the same problem.  (There is no way I can remember the actual problem right now.)   The results are often an error of about 10% difference between my answer key and my calculations.

While we are at this, I have a question I’m stuck on.  Suppose you read a meter stick and you get a reading of 8.65 cm.  That is three significant figures.  Now you move a little ways up the ruler and read 22.40 cm.  The accuracy of the ruler hasn’t changed, but I’m now working with 4 significant figure versus 3 before.  I wouldn’t round the second number, it is as accurate as the device, but the first number isn’t 8.600.  How do you account for this when you are dealing with the significant figures of a problem?


What’s New in 2013/2014?

Every year brings a change, this one is no exception.

I will be picking up the sophomore honors Algebra II class to keep them separate from the juniors. This should help accelerate them and put them on a stronger track towards Calculus. Looks like there will be only one section each of Physics and Calculus, but still two of Robotics & Engineering.

Hot topics this year are going to be the Common-Core Standards, Standards-Based Grading (SBG), improving AP Calculus scores, and somehow adding Python, maybe as a club.

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