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.