Wednesday, January 07, 2009

Doing Gravity

I have enjoyed presenting the science class so far. We covered why science started in Ancient Greece, the first scientific thinker, how the Ancient Greeks knew the world was round long before Columbus attempted to sail to Asia, and spent time covering Archimedes' discoveries in bouyancy and the lever.

The format of the course has left a bit to be desired for me and the kids also. Teaching elementary science to varied ages and skill levels necessitates skipping a lot of math. I also feel that with the lecture format will be more difficult to keep them listening and not distracted as we delve into the modern era of science. I wrote that last sentence prior to actually having class today. Running the class without a lecture to prepare the kids for the vocabulary or flow of the discoveries was probably more confusing for the kids. They did love the demonstrations they could help with.

I started talking about why it was hard to convince people that the Earth was round even with all of the observed evidence--how would people on the otherside not fall off? Aristotle figured that things were attracted to the center of the Earth. I dropped a piece of paper and a ball at the same time, showing that the ball hit first. I then crumpled the paper and dropped them and they hit at the same time. We talked about air resistance and how the ancients didn't realize that gravity would pull on them both the same and weight didn't matter. We rolled spheres of various materials across a smooth floor to demonstrate momentum (top picture). We allowed the spheres to roll down a wrapping paper tube to show how the speed of the marble varied with height. Then we discussed velocity and what constant velocity would look like--traveling the same distance in the same amount of time. Then we rolled the ball down a ramp (an old church pew that's about 10 feet long) with ribbon placed at even distances. The set up is shown in the middle two pictures. After asking the kids to count each 'bump' as the steel sphere jumped the ribbon, it was obvious that the velocity was increasing. I talked about acceleration and force. We then used the handy-dandy nerf dart gun (bottom) to show that horizontal motion and the vertical pull of gravity operated independently of each other. I shot the dart gun and dropped a metal sphere at the same time. The kids watched the dart and could hear the metal ball hit the ground at the same time.

It was fast-paced and packed with demonstrations, but I really missed the lecture. I like making sure they know what's coming. I especially prefer being able to present concepts and vocabulary that they are seeing, perhaps for the first time, when they are not distracted by gadgets or set ups. Perhaps the issues with the lectures are related to trying to get elementary-age homeschool kids to sit and listen when they haven't been in a class before. I should be very clear on my expectations of their behavior.


LB said...

Did any of your students react to Aristotle's name? Three of my six were downright disdainful when I mentioned him! I was shocked. When I asked why, they said he was wrong - and that's that! I tried to set them straight (slightly) that he had been right about a lot of things and his ideas were a beginning.


Kim said...

No, but I also didn't go into Aristotle much. I debated about including Aristotle in my coverage of the ancients and decided not to cover him specifically. Mostly because his contributions to physics were minimal (in his time, that is). We did spent time talking about how we had named one of our cats Aristotle and another Galileo.

I read a book while I was getting prepared for the class that had actual excerpts from the original notes of some of the great scientist's published works, like Galileo, and the introduction excoriated Aristotle! In his view, Aristotle was to blame, somewhat, for the Dark Ages and wholly for the church's persecution of Copernicus and Galileo. The idea being that if Aristotle hadn't been so good and well reasoned and yet totally wrong about physics and cosmology, the Modern Era of scientific thought would have begun much earlier. We know that it was Aristotle's work in logic, induction, and observation in the other sciences that allowed us to break out of the appeal to authority eventually, but I was utterly appalled at the narrow reading Aristotle received from the author. So I guess I cannot be too surprised that kids would do something similar. Obviously an adult should be able to figure out that the essentials were not specifically what Aristotle got wrong, but the fundamental ideas that had been adopted and then actually applied to correct it.

When we covered Thales, we made a bit of fun at Thales conclusions. I made sure, however, to point out that it wasn't what he came up with for explanations that were important to understand but the shift in thinking--mystical to natural based and specific to general--that was why he was considered very important.

LB said...

I only mentioned his name as one of the early thinkers regarding natural laws.

So, maybe those three read a biography of Galileo in which the excoriation of Aristotle played a part. Interesting.

Thales was one of the scientists chosen for a report. I had hoped that by exploring the early thinkers out of class we could use in class demonstrations to support the development of the scientific method.

Amy said...

My college physics professor started off gravity with almost the same demonstration as your dart gun. Then he lectured. I loved it. Any reason the lectures can't come after the demos?

Kim said...


My guess is that the kids are focused on outcome at this point. Not surprisingly, since they probably don't know enough to place enough emphasis on ideas. So right or wrong is pretty much filling their heads. I think your info about Aristotle was novel and gave them something to really consider!


That is a good idea. I could demo, then talk, then maybe let them have a go themselves--when I won't be so concerned about how well the demo works. You can bet I wasn't willing to let them shoot the dart gun though--panic would have ensued!