TIMING BALL StartStopMode switch (Act as Start, Stop function in stopwatch & to display time and height under free fall after impact in mode function). Very easy to use to measure value of 'g'. Very accurate and economical ball.The Timing ball is a unique device that records time from moment of release of ball to the moment of impact (on ground or object). It can be used to conduct a number of experiments involving acceleration due to gravity (g).