Android Pendulums
An example Android device pendulum.Copyright 2013 Douglas Bertelsen, College of Information Science & Technology, University of Nebraska-Omaha
Students investigate the motion of a simple pendulum through direct observation and data collection using Android® devices. First, student groups create pendulums that hang from the classroom ceiling, using Android smartphones or tablets as the bobs, taking advantage of their built-in accelerometers. With the Android devices loaded with the (provided) AccelDataCapture app, groups explore the periodic motion of the pendulums, changing variables (amplitude, mass, length) to see what happens, by visual observation and via the app-generated graphs. Then teams conduct formal experiments to alter one variable while keeping all other parameters constant, performing numerous trials, identifying independent/dependent variables, collecting data and using the simple pendulum equation. Through these experiments, students investigate how pendulums move and the changing forces they experience, better understanding the relationship between a pendulum's motion and its amplitude, length and mass. They analyze the data, either on paper or by importing into a spreadsheet application. As an extension, students may also develop their own algorithms in a provided App Inventor framework in order to automatically note the time of each period.
Harmonic motion is prevalent in the repetitive (periodic) motion found in the rhythms of nature on Earth and in the universe, as well as human-made devices such as watches, clocks, toys and uncountable mechanical systems. Engineers incorporate regular periodic motion into some designs, and must understand and adapt other designs to fit the periodic motion present around them.
After this activity, students should be able to:
- Explain the basic properties of periodic motion (specifically, in a pendulum).
- Analyze Android app-generated graphs representing periodic motion.
- Use pendulum equations to solve problems related to pendulum motion.