Day 32: Physics 10 Journals

Even though Physics 10 didn’t meet today, the journals they turned in recently are worthy of taking today’s post. This class is the only one I am teaching with any students in it who have done this kind of writing before (in their math class last year with me or the other geometry teacher for the half who took that class in 9th grade).

Here’s one particularly awesome journal (just one that I happened to already scan—there were plenty that would have been good examples here). I will put the images of the pages up and transcribe it here, too, to make it a little easier to read. Here’s the transcription first, followed by the original pages, followed my some short commentary from me.

Physics Journal #1

Practice set 1 Problem 2d) Written description: The object starts close to the motion detector, and moves at a constant, moderate speed in the forward direction for several seconds. Then it stops for a few seconds before returning to its starting point, once again at a moderate speed.

My first thought about this problem was to draw the position time graph first. I thought that a visual representation of what was going on would help me graph the velocity and the motion map. When drawing the potion graph, I split the written description up into several parts. I couldn’t just read the problem and draw the graph easily. The first part of the first sentence is, “The object starts close to the motion detector.” Although it isn’t written, I decided that the motion detector could be the origin in this problem. Because the object starts close to the motion detector, but not on it, I made my starting point a couple units above the origin on the y-axis. With my starting point in place, I read the rest of the first sentence. “(the object) moves at a constant, moderate speed in the forward direction for several seconds.” I found this part straight forward. I drew a diagonal line in the forward direction. I then moved on to the next sentence: “Then it stops for a few seconds.” I knew that if the object is at rest, the graph is not linear. So, I drew a straight, horizontal line connecting to my diagonal. Here’s what my graph looked like so far:

Annotations on the graph read: Starting point of object; motion detector; at rest.
Annotations on the graph read: Starting point of object; motion detector; at rest.

Flip the page!

The next part of the sentence is where I got (temporarily) stuck. The object returns “to its starting point, once again at a moderate speed. My initial approach was to literally draw a line back to where it started:

Annotation on graph: starting point.
Annotation on graph: starting point.

After drawing this, I knew right away that it was wrong. But, I thought so for the wrong reasons. I thought that it was wrong because this line returns to the starting point at a faster speed. The problem says the object returns at a “moderate speed.” A moderate speed is the same speed that the object moved in a forward, positive direction, which means that the object needs to move in a negative direction at the same speed. My next attempt was:

Screen Shot 2015-10-29 at 8.00.45 AM

This is where I got stuck again. The object can’t return to the starting point if it moves at the same speed. At this point, I asked Kelly for help. She said, “Someone always makes this mistake.” It was at this point when the answer came to me. The object returns to its starting point, but not literally: in a negative direction. My final graph looked like this:

Screen Shot 2015-10-29 at 8.02.43 AM

Here are the original pages:

R_journal_1 copy

R_journal_2 copy

Here are a few of my favorite things about this journal: 1) She gives a really detailed play-by-play of her thinking. 2) She isn’t embarrassed to share her mistakes; in fact, she sees those as important parts of the story. 3) One of the best parts is when she says she knew she was wrong, but that she thought that for the wrong reasons—that’s a really sophisticated level of thinking. 4) I also love when she says she asked me for help, records me saying probably the least helpful thing I could say, but gets to the right answer anyway.

And that’s where we’re starting with journals in this class. I’m so excited for these kids!

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