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

## Archive for June 2008

### Building a Tetrahedral Kite

Posted on: June 25, 2008

This is a very cool activity. If you look at how this kind of kite is built, you will see it grows like a pyramid. The result is that you have a set number of cells that have to be built to make this work. Here is the link where I got the project in the first place.

http://britton.disted.camosun.bc.ca/tetrakite/tetra.html

Also an NCTM site:  http://illuminations.nctm.org/LessonDetail.aspx?ID=L639

Now for some pointers:

• Think light. Apparently there is a kite season. Good luck finding kite string when it isn’t kite season. I use macramé string I get at AC Moore. The macramé string is strong and inexpensive.
• It helps to precut the strings and the tissue paper. Again, I purchase tissue paper at the dollar store. They have 30 very colorful sheets for … yep, a dollar.
• Rather than tying the ends of the strings together as instructed, I’ve found that it’s easier, quicker, and better if I use a separate small left over pieces of string and just tie the corners together. It’s much easier to get a tight joint and tight connections make for a happier kite.
• I’ve made these kites with 4, 10, and 20 cells. With 4 cells it wouldn’t get off the ground. With 20 cells, only the slightest of winds and we couldn’t keep it on the ground. I like to supersize my science whenever possible.
• Pay careful attention to step 19, creating the bridle. You are going to have a hell of a time making it fly if you don’t put it in the right place.
• I had never seen one of these fly, so I was surprised when I realized they fly upside down. In other words, the point of the pyramid points down. To launch, simply place it on the ground, give the string a slight pull to try to lift the kite onto the point. If there is any wind, the kite will take off into the air.

There is a lot more you can do with this design. The picture on the right is a group effort by a 4th grade class. There is a lot of great information and ideas at their site: http://www.cit.gu.edu.au/~anthony/kites/tetra/straw_plan/

One final point. I could barely get the 20 cell kite through the door. If you are planning on going larger than 20 cells, you might want to plan to build modules and connect them on site, or maybe have a set of double doors to get your monster kite out of the building.

### Big to Small or Small to Big (Rant? Thoughts? You decide.)

Posted on: June 25, 2008

How do you present your material? How do you learn?

I seem to be in the minority of learners, I like to get a big picture, then the details make sense. Am I alone? I can’t understand the idea of studying all the little parts without first understanding what I’m trying to do with them.

I spent twenty years in technology sales. I used to sit through marketing presentations and I kept asking, “But what is the big picture?” They just kept giving me features and benefits. I don’t need a feature or benefit if I don’t know my goal.

Here’s a classroom example: a Biology teacher friend of mine started the students off with single celled creatures, moved to multicelled, to nematodes, etc. It seems to me that I would start with the big picture of a person and teach about the different systems; respiratory, circulatory, reproductive, etc. They can relate to people, not nematodes. Now that you are on system, look at how other creatures get their vital supplies. If it doesn’t relate to me, it’s hard to care.

I try to teach Physics from the big picture on down. I like to build a common understanding of say, momentum. They can’t solve these problems about how fast things are going unless they can see why this matters. I crash things together and show what happens when big hits small, when small hits big, when one is moving or both are moving. When a moving object hits nothing, nothing changes.  We try to get an understanding of the definition of momentum and what has a lot of momentum and what has a little.

While I’m on the subject of momentum, I always do a calculation of what happens to a person in a car and not wearing a safety belt. I let the students calculate how fast they will be traveling when they hit the windshield. Maybe I can at least save a kid’s life by having them wear seat belts.

### Inertia Example #517 – The Sledge Hammer & Anvil

Posted on: June 25, 2008

Do I really have 517 demonstrations of inertia? It feels that way, but of course I don’t. I max out at around 300. Anyway, this is similar to putting an anvil on your stomach and then hitting an anvil with a sledge hammer. I’m just not that trusting. Here’s how I made it safe for High School seniors:

I take a box of books. I have a case of Conceptual Physics books, they weigh about 80 lbs. I have a student come up to my demonstration table and lie down. I like to pick one of my more vocal (translate as annoying) but also smaller in frame kids. They lay on their back and I gently place the box of books on their chest and stomach. When they agree they are not in pain, I usually call up the biggest and strongest kid in the class. His job is to slam his fists down on the box of books as hard as he can. This is usually a friend of the one laying down, so the drama is even better.

As hard as he hits the box, the kid on the table barely feels anything. While he’s still there, I ask them about removing some of the books from the box and what do they think would happen. I like for them to take the thought experiment to the extreme, so I ask if we take all the books away and replace it with a single piece of paper. Then what would happen? My hope is that they see how the large mass has a lot of inertia and resists a change in motion.

This usually moves to about half the class trying this on each other at my table. Chaos, you bet, I encourage it. They are interested enough to get out of their chairs and try an experiment, you better believe I’m going to let them. I’ll take every teachable moment I can get.

### Astronomy Project

Posted on: June 22, 2008

This year I wanted to include a unit on astronomy in my Physics classes. Rather than teach the material myself, I felt this was worth having the students do as a project. I broke the material into the following areas:

1. The Earth
2. The Sun & other stars
3. Space Travel & Space Ships
4. The Big Bang & Cosmic Evolution
5. Inner Planets
6. Mars
7. Jupiter
8. Saturn
9. Outer Bodies (Uranus, Neptune, Pluto, Kuiper Belt, Oort Cloud)
10. Telescopes
11. The Night Sky
12. Exosolar Planets & SETI

The order above is the order I wanted the material presented. While that didn’t work out because students were absent or unprepared, I developed the order so that the subject built on previous presentations. I will definitely keep it the order listed for next year.

Each group or individual had to do a Powerpoint presentation with at least 20 slides. I then gave them a presentation called “How to do a lousy powerpoint” where I did many things wrong to illustrate what NOT to do. It got a good laugh. I told them I wanted well researched information and lots of visuals, including movie files and simulations. To start them on the research path, I provided this page of links: recommended-astronomy-web-links

I had specific areas I wanted the students to include, so I helped them along by providing a sheet with suggested topics. Here is the word document: astronomy-outline-2

The handout is broken into the topic and suggestions specific to that topic. There isn’t a sheet for SETI because a couple of students asked to add it. They did a great job describing the different methods used to detect exosolar planets. The simulation below is a demonstration of the wobble method used to detect planets outside of our solar system.

Students also had to provide a study guide for taking notes during the presentation and a quiz to be given the next day. I ran into problems with trying to fit two presentations and two quizzes into each class period. In the end, I randomly gave quizzes and they were allowed to use their study guides (as was the plan). I need to do something better here. I may up the requirements to 30 slides, then only have one presentation per class period. That would work out better for the quizzes.

No project of mine would be complete without the rubric: Astronomy rubric

Posted on: June 22, 2008

My wife asked me why my Rollerblades were in my trunk. She knows I don’t use them where we live, there are too many hills. I’m a Physics teacher, the answer should be obvious – Conservation of Momentum. Tell me the truth, don’t you look to do something unexpected to get you students’ attention. In graduate school we called it disequilibrium.

You should have seen their faces the day I skated into class. Of course I have the racing bearings which work well for classroom demonstrations. The idea is to start at a standstill and throw a heavy object and watch the object go one way and me the other. I also carried a box of textbooks and while moving forward, threw them ahead of me. They could see that I instantly slowed down. This is what dreams are made of. There will be NO photos, use your imagination.

### Inertia Example #406 – Which String Breaks?

Posted on: June 20, 2008

I do so many demonstrations of inertia, you’d think it would sink in. Anyway, this is a nice little one I usually start a class with soon after I discuss inertia.

The string at “A” is tied to a solid surface. In my room, it’s the TV arm on the wall. String “B” is the same type of string, I usually set it up with two “B” strings hanging down. In the middle is a piece of wood with two eyescrews attached. Around the wood is a pound of dollar store clay. (I really hate dollar store clay, the dyes come out and stain everything it touches. I just don’t touch the clay and this setup goes back in a bag to be used one day a year.)

First, ask the students what happens if you yank quickly on one of the “B” strings. Allow some time for discussion. Inertia of the blob of clay is going to resist the motion of the yanking and the “B” string is going to break. Do it for them.

Part two, tell them you are now going to gently pull on string “B” and ask what is going to happen. In this case, you are slowly applying a force downward. Let’s say you pull down with a force of 10 pounds. String “B” feels 10 lbs of force, but due to the weight of the clay blob, string “A” should feel 11 pounds of force. Yeah, I know, kg, not pounds, but since clay comes by the pound, I wrote in pounds. Sue me. Anyway, string “A” is going to break first because it always has one more pound of force on it.

For the very first time this year, the “B” string broke for both of them in one of my classes. That sure took the wind out of my sails. I cut another piece of string and did it again, although I lost the wow factor. Can’t win them all.

Tags: ,

Posted on: June 18, 2008

Yes, I showed a five minute episode of a Roadrunner cartoon as part of my Physics final exam. The students were instructed to watch it through the first time and maybe jot some quick notes. They were shown the video a second time in order to have enough time to get their thoughts together.

Their task was to identify five principles of physics that are done either correctly or incorrectly in the cartoon. The students needed to identify the principle, explain or define it, then use an example from the cartoon and explain whether or not the cartoon got it right. If they got it wrong, they needed to explain what should have happened.

I actually had three videos, the first was the Apollo 15 video of an astronaut dropping a Falcon feather and a hammer on the surface of the moon. The astronaut says, “Mr. Galileo was correct” as the objects hit the surface of the moon at the same time. I wanted the students to tell me what Galileo was correct about. I got a lot of right answers, but I also got a lot of wrong ones.

The second video was a very old scene from Buck Rogers. I’m talking about the newsreel version, very old and dated. That particular segment didn’t go over as well, the kids didn’t see enough of what was wrong in the show. Let’s just say that I won’t be using that video segment next year.

### 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.

### Polls in the sidebar

Just a quick poll to help me understand who is stopping by my blog.