What Causes the Different Spinning Rates of a Radiometer?

My students often stare in wonder at the radiometer that sits in the window sil of my classroom. A lot of them think it's the temperature that causes the different spinning rates. Others think it's the amount of light. I decided to attempt to see which factor determines it. This could be a good inquiry activity for students and it also demonstrates how smartphones are becoming useful data collection devices.

Motion: A Change in Position

Motion is the change in position over time. Students often have a difficult time understanding that concept graphically, which is one of the big 8th grade science standards.  Vernier's Go!Motion sensor and software are excellent demonstration tools. The video demonstrates how both of them work together. Usually when I introduce it, I just give a volunteer student a big (1 x 1 yard) whiteboard and tell the student to walk towards and away from the sensor. The students can see the graph on the large video screen. They quickly pick up that the farther away from the sensor the student is, the higher on the graph the line is and vice versa. I have them draw graphs what what they think certain types of motion are and then we see if we can replicate the graph. The software also allows a prediction graph to be drawn and then students can see if they can walk that same motion graph. In later lessons, acceleration graphs are explored. Having a class set would be ideal, but having one sensor with a computer hooked up to a video projector will work just fine.