Introduction
Experiments to measure gravity have been part of physics curricula for decades. Examples of direct measurements include (a) dropping a mass attached to a tape which passes through a ‘ticker tape’ machine tapping at 100 Hz, (b) dropping a steel ball, held by an electromagnet at a known height above a switch, and recording the time between the release of the electromagnet and the activation of the switch. Indirect methods include timing a simple pendulum of known length. With the advent of data-logging systems, equally slotted plates can be dropped through the gap in a light gate and the on–off–on intervals can be calculated from the recorded data in order to deduce the acceleration due to gravity