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# homeschoolsciencegeek

### July 2016

We started this week’s class by talking about Newton’s law (again) and how objects in motion continue in motion, as I gave a block on the table a push and we watched it come to a stop. So why didn’t the block continue in motion?  Because the force of friction is also acting on the block.  We also talked about air resistance and how it increases the faster you move.  Think about putting your hand out the car window as you drive slowly in a parking lot – there is very little air resistance on your hand, but if you do this while traveling at 70mph on the freeway  you will feel a very large force from air resistance.  Similarly, walking in knee deep water isn’t too bad, but running is almost impossible because of the resistance of the water.   The students had heard of the term ‘terminal velocity’ but they weren’t sure what it meant so I explained how the force of air resistance increases as you fall through the air because your speed is increasing and at some point the force of gravity pulling you down and the force of air resistance pushing up will be equal.  If the net force on an object is zero than the acceleration is zero and the object will be moving at constant speed, its terminal velocity. We went on to talk a bit more about sky diving, flying squirrels and wing suits!

The lab for this class was “Friction lab #1: How Much is Enough?” from Real Science Odyssey Physics.  Basically the kids put books or blocks on a ramp (plank of wood) and then raised the ramp until the book started to slide.  One student would hold the ramp while another student measured the height and base of the triangle created by the ramp. The lab uses a ratio of these measurements to determine the coefficient of friction for the set up.  I’m not sure the students ‘got’ the coefficient of friction part, but they certainly understood that if the friction force was greater then they had to raise the plank higher before the object would slide.  They used books with and without dust jackets and covered the plank with aluminum foil.  We also used some friction blocks I had made by gluing sand paper to one side on a wooden block.  We had to hold the ramp at almost 70 degrees before the block started to move!!  The lab handout also asked them to devise a way to determine if the weight of the block/book would change the coefficient of friction, which is kind of tricky because the weight of the block does increase the FORCE of friction, but not the coefficient of friction which is a characteristic of the surface.  We found the coefficient to be constant even when we doubled the weight (adding another book or block).

We watched “A World Without Friction” by MITK12Videos on Youtube in class:

Here are a few other vidoes including the friction of curling and a clip from Bill Nye.

We started class by reviewing the first two of Newton’s laws and then talked about the 3rd law – For every action there is an equal and opposite reaction.  If you exert a force on a box, it exerts an equal and opposite force on you.  The lab we did was Lab #6 Rocket Science in Real Science Odyssey Physics.  Basically the students blew up balloons of various shapes and sizes and measured their length or width and then taped them to  a straw.  The straw had a string going through it and was stretched across the room, about 6 meters.  When they let go of the balloon the air would rush out, exerting a force on the balloon that would make it travel along the string.  They spent a good hour doing this and found the more air they put in the balloons the further they would go.  They also found out that water balloons (filled with air)  worked pretty good for this experiment, they were small but traveled a pretty good distance since they were lighter (smaller mass, greater acceleration with a similar force).   To make this lab easier we marked the string ahead of time so the kids just had to count off the marks to find how many meters their balloon traveled. The string had orange marks for meters and blue marks every 10 cm.  It would have taken forever if they had to use meter sticks to measure the string everytime. Here’s a video from one of the data runs.

After they took all their data we talked about the results, answering the questions on the lab handout and then watched the following videos from Veritasium.

I didn’t get to show this TedEd video in class but it summarizes Newton’s laws nicely.

I am going to be teaching a high school honors chemistry class to a small group of homeschoolers next year and I’ve been having a heck of a time finding a textbook that I like, mainly because I’m just not that found of reading chemistry textbooks.  I started with Chemistry: The Central Science by Brown, etc which comes highly recommended but my eyes started glaze over when looking through it and after doing some more digging I found its mainly used in AP Chemistry classes where its the kids second chemistry class.  Most of the kids in my class will have done some chemistry before but this just looked like too much of a leap… at least for me.  So back to the drawing board.

Searching for ‘honors high school chemistry’, I found many teachers use Modern Chemistry and since its available as an ibook on iPads for only \$15 I went ahead and bought it.  Its not too bad and I think my kids will prefer the ibook verion, its much lighter than carrying a huge textbook for one and you can zoom in on the pictures and it even has some short movies here and there.  Personally I like to have a textbook to flip through so I went ahead and bought the homeschool package through the homeschool buyer’s co-op which saved me about \$25 over buying it directily from Houghton Mifflin Harcourt.  This will get me a real textbook, online access to a textbook,  labs and other resources.

I also found a gold mine of resources put together by Ian Guch, a high school chemistry teacher.  I plan on using his textbook, Chemistry: The Awesomest Science, which you can download free on his website.  He has a link set up for donations and since I plan on using a lot of his lessons and his textbook I made a donation.   He says he’s working on a  middleschool chemistry textbook for the fall which I’m hoping he finishes since I’l also be teaching a chemistry class for 10-12 year olds.

The other book I recommend my students buy is the Cartoon Guide to Chemistry by L. Gonick. I love all his books and find them to be a quick and easy read compared to most textbooks.

Students will also be required to have a laboratory notebook.  I require this because I want the students to be able to take these lab notebooks to colleges and prove that they did indeed do ‘real’ science labs as homeschoolers.   Of course the only student to really give me grief over this is my own, who prefers to do a digital lab book on his iPad.  I find this hard to accept but searching the web I found many companys and universities are moving toward digital lab books so I may let him go digital this year.

My kids watch a lot of youtube channels, many of them science related and its not uncommon for them to bring me a video and ask if we can do the experiment/demo shown on the video.  Well, now that they are both teens it appears that I’m not needed any more. My youngest (13) asked me for a bulldog clip and I saw him wandering around the house with a ziplock of water… hmmm.  A few minutes later he proudly showed me his ziplock full water and pencils and toothpicks.  Cool!

We started class by talking about what it means for an object to have momentum.  The kids knew it had to be moving and they also knew that a massive semi truck moving at the same speed as a small car is going to have more momentum.  So right there we have it all, momentum increases with speed and with mass.  First we did the Real Science Odyssey Physics  (RSO) lab, Giving the Gift of Momentum, where the kids thought about what would happen when they rolled a marble down a track into another marble that is sitting at rest. Then they did the experiment and recorded what happened.  They then thought of other experiments to do, basically different collisions between marbles of different sizes, different numbers of marbles, or having them  moving at each other.  Instead of using cardboard tubes the kids made paper marble tracks and taped them together.  I had thought we might be able to spend some time making a paper roller coaster from the templates I had bought last summer, but when my son and I built one the day before class we found it took too much time.  It wasn’t too hard, but it just takes more time than we have in one class, especially with  younger kids.

Using the glider carts on the air track we repeated some of the marble experiments but with no friction it was much cleaner – the first cart comes to a stop as it transfers all its momentum to the second car.

Then we went outside to complete the second part of the RSO lab, where you drop balls individually and then stack them on top of each other with the smaller, lighter ball on top.  Here are the videos from our class doing the experiment.

Physics Girl has a great video that explains why this works, so after we finished trying it ourselves we came in and watched this:

We also watched the first half of this video on the physics of car crashes,

and this lego stop motion movie about Newton’s Laws.

We also played with a Newton’s Cradle all through class and discussed how it was transferring momentum during collisions.  Next week, Newton’s 3rd law.

HOLLYWOOD ( and all that )

hanging out and hanging on in life and the movies (listening to great music)

Learn from Yesterday, live for today, hope for tomorrow. The important thing is not stop questioning ~Albert Einstein

graph paper diaries

because some of us need a few more lines to keep everything straight

Evan's Space

Wonders of Physics

Gas station without pumps

musings on life as a university professor

George Lakoff

George Lakoff has retired as Distinguished Professor of Cognitive Science and Linguistics at the University of California at Berkeley. He is now Director of the Center for the Neural Mind & Society (cnms.berkeley.edu).