Saturday, November 29, 2014

Circular Motion Simulation

I've been through several variations of circular motion paradigm labs over the years. Lots of approaches, lots of pros and cons.

Here's where I'm landing this year:

  • Preliminary investigation: a qualitative exploration, using basketballs and "science hammers" (lab rods with clamps on the ends) - differentiating between the effects of forces parallel to and perpendicular to the velocity. This establishes the conceptual foundation of uniform circular motion, and comes back later in the year during the energy transfer model (work)
  • Quick conceptual investigation: using either a visual accelerometer or a wireless dynamics probe/LabQuest, determine the qualitative effects of various variables on the acceleration of an object in UCM. Narrow it down to radius and (linear) speed. Angular speed can be a more natural variable for this (and easier to design an experiment to control for), but I've found that students have a lot of difficulty differentiating between angular and linear speeds at this point, and that they later confuse an angle in a banked turn with the angle "around the circle." 
  • While designing a real-world experiment with constant angular velocity is easier, using an applet can make experimental design with linear velocity as a variable just as easy. It's also quicker and more reliable (whirligig experiments can be a little dicey with data quality), putting the emphasis on the data analysis. (Save the whirligig for a practicum later!)
The various circular motion applets that I've used before are pretty much inaccessible now, because of Java's waning usability. So, I wrote one using Glowscript

Here's a screenshot - click through to use the applet.