This rig employs a pendulum to demonstrate acceleration due to gravity. The pendulum may also be used to illustrate simple harmonic motion, conservation of energy, differential equations, linearisation and vectors.
The rig consists of a webcam, a variable-length pendulum, a movable carriage (to set the pendulum in motion) and an ultrasound rangefinder (to measure the position of the pendulum in motion). The period of the pendulum may be determined from the ultrasound data which then allows a calculation of 'g', the acceleration due to gravity. Three versions of the experiments are anticipated: a single measurement (high school physics); multiple measurements but treated as a simple pendulum; and multiple measurements but treated as a compound pendulum (first year undergrad).