# #modphys 25/180: Water Tower

Adjacent to the (beautiful) apple orchard behind our school is a disused water tower. A conveniently-located platform is approximately 25 m above the ground. I was able to obtain permission to access the platform.

I’m keen to use the tower for several classes. In math, we’ll make some angular measurements to determine the height of the platform. For my physicists working on the Constant Acceleration Particle Model, we’ll drop some objects and measure the acceleration of gravity.

Do you have any ideas I could try?

# #modphys 24/180: A €2 Dynamics Track

We have been working on the Constant Acceleration Particle Model over the past week. I introduced the topic using video analysis with LoggerPro, but unfortunately we haven’t been able to get convincing v/t graphs. I suspect a combination of clumsy fingers, air resistance, careless clicking, and LoggerPro’s obnoxious approach to derivatives (second order Newton-Raphson?). Combined with the need to prepare for a practical, it was time to go tangible for the deployment lab.

I really wish I had a proper dynamics system, but unfortunately the money just isn’t there. I spent a lot of time rolling carts, cylinders, and balls down ramps before I discovered that the Vernier motion detector works just fine inside a pipe.

For some reason (perhaps a type of resonnance?) the face of the motion detector needs to be slightly off-center. But I was able to detect a marble within the pipe above to about the length of the 3 m pipe. The graphs from this motion are below. The a/t graph is pretty noisy, but I think I could convince myself of a constant value. The v/t graph is clear enough to show the effect of rolling friction.

I also tried one of my plastic cars in a larger pipe (formerly used for a perfume diffusion experiment, so it retains an aura of synthetic mystique). It seems to work well. The wheels roll only on their outer rims, which should help to reduce frictional effects and keep the car moving straight.

# #modphys 22/180: Constant Acceleration

After two weeks of picking up skills — proportional reasoning, LoggerPro — we spent today’s class in board meeting (with a couple recesses to work up things) assembling the Constant Acceleration Particle Model. Unfortunately, for a variety of reasons, we didn’t get really convincing values for 0.5a, a, and 2a on the x/t, v/t, and v/x graphs. We used video of a plastic orange being dropped from a height of 3 m. I had hoped for a digression about terminal velocity (the last 3 frames, generally) but there was too much else to chat about.

Afterward, we started worksheet 1, from the modeling materials. It is, in many ways, a re-hash of the same process. I think this is valuable because I think some of the meaning was obscured with new technology (LoggerPro) this time around. By the end of class, most students were about halfway done. Since the task wasn’t new ideas, the students didn’t need much support, and it wouldn’t take more than 30 minutes of honest work to finish, I assigned the rest of the worksheet for homework. We switched to Managebac this year and, judging by students reactions, it seems to do a great job of listing their tasks and homework.

I am looking forward to deploying the model next week as we solve problems. Highlights will include misconception hunting, trying
king forward to deploying the model next week as we solve problems. Highlights will include misconception hunting, trying out goalless problems
out goalless problems, and getting the students to take more risks and initiative in board meetings.