Wednesday, May 4, 2016

Day 153: Balancing Act

I've generally found that if I want someone to understand a concept, it's better to show them than to tell them.  Since I've been teaching two new subjects this year, I haven't been as prepared to do demonstrations and labs as I would have liked.

Today, however, we started our physics lesson on torque and I made the time.  Torque is, I think, a fairly difficult concept for students to understand.  Most of the time, we've just spent 6 months talking about forces have to be balanced and then along comes the idea that objects of different mass can balance each other if they are spaced well.

I set up some examples around my room.
The large mass is 20 times the small mass

2 kg balanced against the weight of the board itself

8 kg balanced against the board

Large mass is 10 times the size of the small one, fulcrum is at the center of mass of the board

As the students came in, there were told "DON'T TOUCH ANYTHING!!"

As a group, we walked from station to station.  I talked about the set-up and asked what they thought would happen if I moved one of the masses.  In several cases, I showed them how the entire system could be unbalanced simply by blowing on the end of the board.

When we finished with each station, I dismantled it methodically and had a student replace the force with their own hand to examine how much force was actually being applied.

After a brief discussion, I closed the class by having them watch a video of Lara Jacobs.

The majority of this section will involve basic seesaw and balance problems, but, rather than a final test, they will be asked to design a modular seesaw.  The rough version of it will go something like:

Design a seesaw for a playground or back yard.  This seesaw should be useable by any number people, regardless of individual mass.  It may have moving parts, or special designs, but should be organized in a way that will tell someone where/how to sit so that, provided they know their mass, the seesaw will be functional and balanced.

In the next few days, I think about a better to work this.

I like this idea MUCH more than a chapter test.

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