Development of gravitational acceleration measurement set up based on laser beams

Abstract

In this paper, using three parallel laser beams system we have calculated the value of gravitational acceleration (g) by deriving a simple equation, where there is no velocity term, is reported. The numerator of the equation is always positive irrespective of distances. The setup consists of commonly available three red laser light-emitting diodes and three sensors using very common fast transistors. A free-fall object intercepts the laser beams to produce three voltage pulses across the collector-emitters of three transistors. These voltage pulses are fed to a storage oscilloscope for measuring the two time-intervals between two subsequent gaps of three laser beams with millisecond resolutions. Time intervals are also measured by two-microsecond timers in microsecond resolution. The object may fall from any height above first laser beam, but the 'g' calculated remains the same. Measurements were done by letting an object fall from two different heights, six times from each height, and the average value of 'g' of 9.8036916315 meters per second squared is calculated using the data of two-microsecond timers, which has a 0.03% deviation from the standard value of 9.80665 meters per second squared. Results obtained using microsecond timers are more accurate than that obtained using oscilloscope millisecond data.