Archive for October 2009
I kind of made this one up, kind of adapted it from the electronic timer manual. The idea is that we use a ramp to accelerate a steel marble, have it pass through timer gates, measure the distance between the gates and calculate the velocity. Do that a couple of times for accuracy.
Now measure the height of the table using a meter stick. Use a fishing weight on a string to find the point directly under the edge of the table. We now have the horizontal velocity, the height of the table, we can calculate how long it will take to fall. Next we do the math and place a penny where the steel marble should land.
In the beginning, it would works sometimes, but not always. I determined that our heavy epoxy table tops caused the steel ball to bounce, losing some of its horizontal velocity. The bounce was easily dampened by placing two or three sheets of paper under the end of the ramp. We also had some issues with hitting the side of the photogate. Lining up the gates with the ramp was a minor issue, but an important one. After the speed was determine, we moved the photogate away used the already calculated speed.
Here is the Lab as I wrote it up, it needs some updates like the paper under the ramp. I realized later that I should have had the kids measure the starting height of the ramp. Then we could go back to it later when we do energy and analyze the results.
Next year I think I will have them hit the penny first time, then a dime, then a small washer, so each time it must be more accurate.
As always, comments and ideas are welcome.
I don’t know why I’ve never mentioned this before. In my room I have a bookshelf full of mostly paperbacks. The books are there for the kids to take, read, and if they chose, return. I go to the public library every couple of weeks, they are constantly selling paperbacks at either 5 for a dollar or a bag for a dollar. I must have about 200 books on my shelf right now.
I have lots of science fiction (Asimov, Bradbury, Clarke, Card), mysteries, thrillers (I love Ludlum novels), fantasy, even some non-fiction titles. I have a bunch of the Sue Grafton series (“A is for Alibi”, etc.) since the protagonist is a woman detective. I often recommend those to the girls. I try to keep the books different from those they read in their English classes. Books don’t equal homework.
I require nothing in exchange. I ask them what they like, then I recommend something if I can. Today a student took Stephen King’s Night Shift. I pick up every copy of that I can find, it’s a great book and I recommend it frequently.
I even have one student who is constantly bringing in books her father donates to my library.
My goal is pretty obvious, get them to read something. Anything. If they are reading, they are learning.
We are using the carbonless lab notebooks, I like them. I want the students to use a lab notebook, but I don’t want the experience of learning to be about rewriting a procedure. I’m struggling with the whole idea that every lab starts out with a hypothesis. My personal experience of learning often begins with “I wonder what happens if …” You could say that is a form of a hypothesis, but it is really just a quest for understanding the workings of everything.
The other day we did a lab where we used a ticker tape recorder to make a mark every 1/60th of a second on a paper strip. The goal is to record the changing distance of a falling object and the constant distance of a constant velocity toy car. I wanted them to see a visual record of acceleration, to understand the distance changes at each tick, and to graph the distances over time. They struggled to write a meaningful hypothesis. How could they write one, they don’t know what they are going to see. I wanted to help them, but I felt that if I said too much, I would be revealing the discovery they should be making.
If labs are about discovery, and I think they should be, then how can they have a hypothesis? How is it discovery if there is only one right answer? If I make the lab all about them finding the right answer, then their focus is on what will get them a good grade, and not about learning physics. I’ve looked at lots of lab report formats online. They make sense if the experimenter is doing research on a topic where he or she is actively working. Each bit of learning leads to a new question and a new experiment. Here, the hypothesis feels contrived.
Would it be wrong to have a hypothesis that is just a general question? Am I going about this the wrong way? I think I’d be happier if they wrote, “We are hoping to see visual evidence that differentiates a constant velocity and accelerating velocity.” If I head this way, am I failing to preparing them for college?
One thing I am changing; in the future they can reference the handout. It’s a waste of their time and mine when they have to rewrite my instructions. Yes, it forces them to read the instructions, but that’s not deep and meaningful learning. The clock is ticking.
What are you doing?