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What you need for Physics labs

IMG_5800I went through my list of labs and made a list of all the things we used and thought about what a family could do if they were just doing physics on their own and didn’t want to spend a lot of money.  My first thought is that everyone should buy the Optics Discovery kit, its the best $25 I ever spent. I’ve used the materials in that kit over and over and over again.  It also comes with nice instructions for quick experiments.  If you buy this kit you’l have optics well covered.   A Snap Circuits or other electronics kit could be used for electricity, but if you’re kid isn’t that interested in electronics you can make do with a few batteries and flashlight bulbs for some simple circuits or use some apps/websites for virtual circuit labs.   For mechanics you can do a lot with just an iPad and the Video Physics app, along with a ruler/meterstick and a ball, toy car or marble runs.  Here’s a list of equipment that’s useful for a year of physics labs. I left off the more expensive items like the air track and Go Direct sensors that I use with my classes that aren’t necessary.  I also left off some of the equipment for labs that I didn’t feel worked all that well or could be left out.  Items that are bold are things that I feel are required for a minimum physics lab experience.  I probably missed a few things but this list should at least give you an idea about what you need to do the physics labs discussed in my blog.

slotted weightsMechanics:

Pressure/Gases/Phase changes:

Waves:

Optics:

Electromagnetism:

Nuclear Physics:

  • M&Ms or pennies for radioactive decay activity
  • Spectroscope analysis kit $26  (this is a very cool kit and has enough chemicals that you can use it many times, like when studying Chemistry, or share with fellow homeschoolers).  You can use a candle for your fire source if you don’t have a burner.   – can be done as part of Seeing Color lab or when talking about atoms.

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R2 Physics 33 – Student Presentations

The last class for this course was originally scheduled for 3 weeks ago but my household got a nasty bug and we had to cancel twice.  For this class students gave short presentations (5-10 minutes) explaining how something works.  Some of the topics were Uranium glass, how synthesizers work, laser removal of tattoos, and the physics of fouette turns (ballet).  I passed out smarties candy to students who asked good questions at the end of each presentation.

I’m not sure I would use the same book, How Things Work the Physics of Everyday Life, again. I just didn’t enjoy it very much, and not sure it was a good choice for 9th-10th grade.

This summer, I’m going to try to write up a list of labs and supplies for a family to do high school physic at home without having to purchase a lot of equipment.

 

 

R2 Physics 32 – Nuclear Reactors

Students read 15.2 Nuclear Reactors in How Things Work the Physics of Everyday Life and watched the following videos before class:

We also watched these two videos in class:

I actually managed to borrow a geiger counter for class, along with a few dishes from the 1930s that are slightly radioactive.  I also have a small sample of uraninite that was purchased at a rock and gem show.  IMG_6178Students used the geiger counter to measure the radiation in counts per minute (cpm) as a function of distance from the sample.  The cpm drops very quickly which shows the radiation exposure will depend very strongly on the distance from the source.  I gave a slideshow at the beginning of class explaining how different types of reactors work and how we measure radiation doses and how different doses compare with this chart on wikimedia commons. I wanted to make sure they understood that being near the samples today was not dangerous and that it was way less exposure than a simple dental x-ray.

 

cpm vs distance
CPM vs distance

We also built a small cloud chamber and I’ve talked about that before in this post on nuclear chemistry.  It didn’t work very well today, I think my isopropyl alcohol was a bit old but we did seem a few tracks.

 

 

 

This was the last class covering new material in the book, next week the students will be giving presentations on how something works.

 

 

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R2 Physics 31 – Nuclear Physics

Students read 15.1 Nuclear Weapons in How Things Work the Physics of Everyday Life and watched the following videos before class.

or if you prefer Tyler DeWitt, he has a nice video on fission.

In class I did a slide show on nuclear weapons, explaining a bit about the Gadget, Fat Man and Little Boy, the first three nuclear devices and how they worked.  I had recently visited the National Museum of Nuclear Science & History in Albuquerque, NM so I showed a few slides from that trip.  This is a great science museum if you’re at all interested in nuclear physics and the Manhattan Project during WWII.IMG_5572

The Gadget was the first atomic device, built at Los Alamos and tested at the Trinity site on July 16th, 1945.  The photo below right is a model of what it looked like.  It was an implosive fission device where explosive charges placed around a sphere of plutonium would cause it to collapse and reach super criticial mass.  Fat Man (yellow and black bomb in the photo below left) was a similar design as the Gadget but Little Boy (longer green bomb in photo below left) was a gun type device which fired a ring of subcritical mass of Uranium onto a cylinder (another subcritical mass) of uranium.  Together they reached a supercritical mass and would release enormous amounts of energy.  This design was fairly straight forward and was not tested before being used at the end of WWII.

 

This video explains how the two designs work.

For the lab activity, I gave each student a cup of M&Ms (roughly 120 or so) and told them they were radioactive nuclei.  When they poured the M&M’s out into a tray, all candies with the M showing on top had decayed and were to be disposed of (eaten).  They then IMG_6083 2counted how many nuclei they had left and repeated the experiment until all the nuclei had decayed.   In this activity each toss of the candy is a half-life, the time it take for half of a radioactive sample to decay.  Student predicted how many candies they would have left after each toss and I heard quite a few shouts when they got it exactly right.  We kept track of everyone’s data on a white board and added up the total number of nuclei (candies) that did not decay after each half life (toss) so we could graph the population of nuclei for all the candies as a function of half life.  We got a beautiful decay curve.  Some students graphed the data by hand and some used their iPads to make a graph.

mm curve 2

You can also see in the data table that we lost roughly half the M&Ms with each toss.  A number of students discovered at the end that the candy that was left didn’t have an M on it at all!  Guess it was a stable isotope…. until they ate it.  If you student has food allergies or you just don’t want to use candy, this can be done with pennies as well (I did it that way when we did chemistry), but the students are definitely more interested when it involves chocolate.

There is a movie with Paul Newman called “Fatman and Little Boy” which is about the Manhattan Project  which is pretty good and I recommend my students try to see it.

 

 

R2 Physics 30 – Forensics

I bought the Lyle & Louise: The Jagged Edge Glass Fragment Identification Kit a few years ago and never got around to using it, so today we finally used it.  The Lyle & Louise forensic science kits all center on one murder mystery and each kit has students process one piece of evidence, in the this case we looked at the index of refraction of glass fragments to see if the broken headlight of a truck matched glass found at the scene of a car accident.  Previously, I’ve used the Lyle & Louise Bad Impression Bite Marks Analysis Kit, where students made bite mark impressions of their own teeth and learned what to measure and look for in comparing bite marks.  You can see my previous blog post on using the bite mark kit here.  These kits are interesting but you can’t solve the crime by just doing one or two of them so you don’t get a very satisfying conclusion at the end of the day.  They’re also kind of pricey for a homeschool class, running over $100 each, a few are even over $200.  They do have a small class edition now that includes a bunch of the kits but only for 1 to 6 students, if I hadn’t already bought the other kits I probably would have gone for that one.   If you have a high school student seriously interested in forensic science it would make a nice lab to go along with a semester long class perhaps.

IMG_5952For the glass fragment identification lab, students had to place a bit of pulverized glass on a microscope slide and then a few drops of liquid and a cover slide.  The glass samples come in the kit already pulverindeized and labeled (bottle glass, headlight glass, etc).  The kit also comes with three different liquids with different refractive indexes, 1.45, 1.47, 1.49.  By looking at the glass fragments in these different liquids you can tell if the index of refraction of the glass is greater than or less than the index of refraction of the liquid.  The way you identify if its greater or less than the liquid’s index of refraction is by observing the Becke line – a thin white halo around the glass fragment and how it moves as you change the focus of the microscope.  Here’s a video that shows what it looks like.

I actually did all 4 glass fragments in all 3 liquids provided by the kit the day before class and didn’t see much difference in any of the results so I looked up the index of refraction for common household liquids to see if we could do a few more liquids to pin point the index of refraction a bit better.   I discovered that a number of essential oils, such as clove, cedarwood and cinnamon all have indices over 1.50 so I asked students to bring in any oils on the list that they might have.  This allowed students to find a liquid where the Becke line moved away from the glass and gave them an upper limit on the index of refraction.   Because we only had two microscopes for 9 kids, I split the students into 4 groups and gave each group one of the glass samples.  They shared their data at the end of class.  We never would have finished if every group had to do all four glasses and 3-4 liquids.   You will need to have a microscope for this kit, you can read about our microscope here.  This kit was pricey but I still have plenty of materials to use it over and over again since its designed for a larger class.  Even though we may not have solved the mystery, I think these kits are nice because they show how science is used in the real world in a way we don’t usually think about.

 

 

 

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