I remember using them extensively in my two Mechanics classes during my sophomore year in Mechanical Engineering. They changed my life and understanding of the world. Combined with a knowledge of materials, they informed the way I see the objects in my universe.
I was forced to assign positive and negative signs to everything so my (easy) problems looked like this:
And I used to require that my students do the same. But why must we use negatives?
They get dropped by accident. They require more thought. And they're not necessary in this case. We could just use the bottom half of this picture instead of the top:
I know. It's a tiny change, but the thought process is different. If the up forces balance the down forces, the ups go on one side and the downs on the other - no need for negatives and you get the exact same equation with the exact same answer.
My students are more successful without the negatives. The balancing idea makes sense. And I treat the second condition for equilibrium the same way.
I now use the bottom method - balanced torques. It's a slight tweak, but it works better for student understanding.
I'm not making a lot of little engineers: I'm just trying to get kids to understand their world. But maybe if we make it a tiny bit easier we can inspire one more kid to stay in science.
No comments:
Post a Comment