## Monday, April 11, 2016

### Simple Machines: Levers

For our simple machines work I am combining the relevant lessons from Building Foundations of Scientific Understanding and the lesson planning guides that came with my simple machines,

This post does contain affiliate links.  Thank you for supporting our homeschool.

The BFSU basically says to "go big or go home" and suggests lifting the teacher's desk, while the teacher is sitting on it, with a brick and a 2x4.  Very Montessori in spirit a la the big impressions left by key experiences and charts.  We don't have the kind of furniture they had in mind for that so I put our full set of  Power Blocks in a box.  This weighs about 50 lbs.    We started by trying to lift the box with just our bodies.  Not surprisingly my 48 lb child could not lift the 50 lb box.

Next we tried with the recommended brick and 2x4.  We have lift off!  By the way, we experimented again a different day and found that a cylindrical fulcrum worked a lot better if you can find one.

We experimented with changing the position of the fulcrum thereby creating lever arms of differing lengths.

The distance that we were able to lift the load varied according to the lengths of the lever arms.  The boys measured and recorded the heights we were able to achieve.

I found levers all over the house and some of them were small enough to put on a rug.  Others were not.

It was hard to figure out how some of these function AS levers without a little help.  I contacted my friend Jennifer at the Montessori Print Shop and she sent me her downloadable file for simple machine cards.  I received this free of charge so that I could use them and tell you about them here.

We started with the cards that had the load, effort, and fulcrum labeled and matched them to the real levers we had in the house.  I was able to find an example of just about everything pictured (except my bicep is not nearly that big).  Eventually the boys realized that the levers could be classified according to the position of these parts and they classified them under the picture and definition cards that come with the set.

Then we moved on to using the simple machine models in our classroom.  First we worked with a simple lever.

The boys used some labels I made to label the parts of the lever as well as the eventual parts of the equation they would discover (Fxd=fxD).

I'm so sorry about the quality of these pictures.  The boys love to do their work in front of the window and the contrast there makes it impossible for me to take pictures that look lit.

Here Kal-El is using one of the Montessori Print Shop card sets to classify the different levers and then labeling the parts.  The MPS printable has the labels as part of the file but I amped things up a little.  I don't like picking up pieces of paper that tiny.  I made our out of some Woodsie shapes and Foamies shapes I already had and didn't even need to cut.  I wrote the letters on with a permanent marker.

Here you can see he's matched the control cards with the cards he labeled.  In this post we've only use the cards from the set that have to do with levers.  You can see the complete list of what is included here. For the levers we used definition cards, lever-class definition cards, unlabeled photographic cards of levers, labeled photographic cards of levers, line-drawn images of each class of lever, and a control chart for the classes of levers.   As we study more simple machines we will use more card sets and eventually be identifying the levers from among mixed sets.

They used the lever-part labels to label the parts on our actual levers after labeling the photographs.

Truman likes to label levers too.  #montessoridog

...but it makes him tired.

When he is not busy labeling levers, Truman likes napping and playing with the football the Easter Bunny brought him.

Next we moved on from the simple lever to the "fulcrum balance."  This clever little model has sliding platforms so you can discover how to reach equilibrium by changing the distance of the platforms from the fulcrum.  As per the instructions that came with the model I labelled the platforms "1" and "2" and also drew intersecting lines to mark the center of each platform.

The first day we simply explored how to balance two objects of differing weights and observed which of the two was closer to the fulcrum.  We also observed that if you change the distance of one object from the fulcrum you also had to change the other.

You can't really use this particular model to learn Fxd=f=D (explanation).  I tried this with brass weights and measured distances. The reason is that center of gravity has to be below the fulcrum (torque=mass x gravity x length explanation).  But what you CAN do (as suggested in the BFSU) is make a hanging balance using a ruler, string, and use paperclips for weights.

The boys were able to use this hanging balance to balance differing amounts of paperclips at various distances.  I labeled the different sides of the balance "A" and "B" with a dry erase marker to keep things consistent.

Instead of telling them the equation, the boys were allowed to discover it.  Have I ever mentioned that BFSU is very Montessori?  They recorded all of their data in their notebooks.

I recorded the same data on our whiteboard.  The squares in the question mark columns were originally blank.  We just recorded the weights and distances.  After they were all recorded I asked the boys to multiply the weight times the distance on each side of the balance for each example.  They discovered that the products were identical and wrote the equation.