An economic time-to-amplitude converter has been designed and built, able to measure time intervals of the order of milliseconds. Its main output is a positive signal proportional to the measured time, appropriate for a multichannel-analyzer input. As an application we have measured the transit time Δt of a vertically falling Ping-Pong ball across a small Δx gap, for different heights of release up to 17 m. The dependence of the speed Δx/Δt on the fallen distance is well described by the model of air resistance proportional to the square of the instantaneous velocity. The measured terminal velocity is 9.5 m/s, 98% of which is attained after falling 12.5 m.
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Brandan et al. (1984) studied this question.