08 summer - katie b, dana
uniform vs. nonuniform motion

Overall, this lesson was a good start towards what we wanted our students to understand—the difference between constant and not constant motion. There were several points where they struggled, and we have modified the lesson to address these points.

Prelab

In the lesson before the lab, we are using an activity called “graphing motion” which introduces students to the shapes of position vs. time graphs, and how they can show positive, negative, and zero motion. Dana used this before, and Katie used this after the lab, and Dana seemed to have a better experience. Even so, students’ misconceptions about these graphs showing hills and valleys rather than forward and backward motion persisted. We believe that by changing the lab experience away from marbles and towards more realistic situations, we may be able to overcome this misconception.

The prelab questions we wrote previously for the lab worked well. We do not feel we need to change these.

Data Collection

The students had difficulties timing the short segments of the marble’s motion (in some cases around a quarter of a second). Not only did this affect the group’s data, it also discriminated against some students who did not have the coordination to use the stopwatch (including students with disabilities). Students took no ownership in a marble traveling down a track. Marbles were boring—people, matchbox cars, etc. might provide more interest and more investment. Other than this, they did better than expected while collecting data.

Analysis

Blah! This was bad. We couldn’t ask our planned questions because the students had very little understanding of what the data related to and what it represented. Once they realized they needed to read instructions, they could build the graph and plot the points, but still struggled tremendously with calculating slope. They did not question their calculations because they had nothing to compare the values to, or to check themselves and see if the numbers made sense. Most students could determine the unit for slope, but again, did not connect it to anything concrete. During the non uniform motion, the velocity vs. time graph really was pointless (Katie didn’t even do it) because if they had no understanding of the purpose of the position vs. time graph, then this one meant absolutely nothing. For our purposes of developing this concept, the extra graph is not worthwhile; it only serves to confuse the students more. We also found that we need to spend more teacher-directed time assisting the students with analysis. Instead of giving them more time as a group to work, we will change the organization to have some whole group time, then shorter periods (10 minutes) of group work, then bringing back together the whole class to discuss. This will keep them more on task, and hopefully lessen their frustration.

Assessment (pretest and unit exam)

We agree that having a pretest for this unit is necessary and useful. The Diagnoser questions are written well and require deep thinking on the part of the students, and hit upon the concepts we are interested in. They are, however, written in a manner which we believe is intimidating to our level of students. We have concerns about their scores on these questions, because we are not sure if they are measuring their level of understanding or their level of reading comprehension. Rewriting these questions, making them shorter and less formal may give us a better picture of their true understanding of motion. We both experienced low scores on the unit exam. Again, we cannot be sure what influenced these low scores specifically. Most likely, it is a combination of lack of understanding (seen from the lab), reading comprehension difficulties (from wording of questions), and motivational issues.

documents and resources

• lesson - changes to motion lesson

(c) 2009 ronnster/oharanator productions