Discussion and Conclusions
With the aid of our flashing LED assembly, we have updated the traditional free-fall experiment. However, we have not relied on a computer for data collection. Instead, the students begin by recording the data using a digital camera and complete the experiment by graphing and analyzing the data using a computer.
Once each lab group completes the analysis, we suggest calculating a class average, which may then be compared to the accepted value for g. In addition, regardless of which instrument is used to measure the period of the LED, either a frequency-meter or an oscilloscope, we recommend that this measurement be carried out in a large group setting prior to the start of the experiment. Finally, it may be interesting for students to explain why the falling LED produces bright lines in the photograph, even though it is essentially a point source. And why should the length of these bright lines increase as the LED falls? This sort of qualitative discussion is often left out, yet it is an invaluable part of the learning process.
The flashing LED assembly produces very precise time marks that can be used in other kinematics experiments. By attaching a parachute to the assembly it is possible to study air resistance and terminal velocity. The assembly attached to a string can be used to study the motion of a simple pendulum. Equally interesting is its use in the study of the motion of an object on an inclined plane.