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.