Thursday, July 24, 2014

Southwest Michigan Modeling Workshop Day 15

The last day of the workshop started with a breakfast prepared by the participants of pancakes, bacon and sausage!  It was a great way to end the workshop but it got us kind of a slow start.

Reviewing our circular motion idea from the previous day we started with a demonstration where I spun a stopper over my head and released it!  I asked for observations of where it went.  I did this several times with a stopper basically flying around the classroom!

I had them then draw a motion map for the stopper.

We then reviewed the aspects of circular motion that constitute the model.
With the major ideas in agreement I asked them to draw force diagrams for three specific situations:
1. A rider on a merry-go-round (not the one with the horses)
2. A rider on a loop of a roller coaster
3. A rider on a carnival ride called the rotor or the gravitron

In each case the unbalanced force must point toward the center!
Here is where things got interesting.

We know that the unbalanced force points toward the center.  In my classes we call this the Funbal.  Some people call it the Fnet.

Here is the key to getting this - there is a vocabulary word that is associated with this unbalanced force.  It is called the centripetal force (let's use Fcent).

The idea is this:
Funbal = Fnet = Fcent

They are all the same thing!  I gave each group a stopper on a string and asked them to spin them around and feel the factors that they think affect the force they are feeling.

Each groups comes up with the idea that more speed --> more force and that more mass --> more force.  In addition each group had an idea that the changing the radius had an effect on the force but couldn't decide if more radius meant more or less force.

So we asked them to put the three variables into an equation that made some sense to them and show how the units worked out to N.

Not the best way to do this but a quick and dirty way.
After that we checked with the Google.

They then got to work on unit 8 worksheet 1.  This was a serious struggle for them but mostly because it is really hard.  The circular motion unit is a culmination of every model that we've developed through out the year/workshop and is at the limit of most participant's understanding of physics.

I then hung the Flying Pig and asked the participants to find the tension in the string holding the pig.

It is an easy practicum challenge but the kids like it!

Then we set up a hard practicum challenge.

The idea is simple.  We gave each group 3 or 4 pieces of string.  They tested the strength of the string.  Then they created a pendulum with a mass of their choosing at the bottom.  They raised to an angle they calculated and let it swing.  Then they raised it 10 degrees and as it swung it had to break.

This is a little challenging but they got it to work!

And all of the sudden we were done.
We gave the FCI post test and had the participants do the end of workshop evaluations.
Then we cleaned up, gave out door prizes and headed off into the sunset.


Hugh Ross said...

Where can I get a flying pig?

Don Pata said...

You can get one from Arbor Scientific:

They are fun, cheap and fragile (must be Italian).

They are located in Ann Arbor, MI and can get one to you quickly.