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Principle of the experiment : to measure the time taken for a stell bar to drop through a known height, and to calculate the acceleration from this.
Calculations : Since s = ut + (1/2) at 2 , and initial velocity u is 0, the formula can be rewritten as s = (1/2) at 2 . Also, displacement ( s ) in this case is the height ( h ) and acceleration ( a ) in this case is g , the formula can be rearranged into g = (2 h ) / t 2 .
Accuracy : To determine the accuracy in the result, we can compare our answer with the theoretical value of g , which is 9.8 m / s 2 . The closer we are to this theoretical value, the more accurate our result is.
Precision : Because the starting and finishing of the timing is done through the sensor, it makes sense to record the time in milliseconds. Also, the precision of the measurement can be determined when comparing different data; the more similar the data are with one another, the more precise the measurements.
Dana Lin, AS3 October 2009 Systematic errors arise from the equipments used. As long as we ensure that the timer starts at 0 and there is no reaction time between the light sensor and the digital stopwatch, the systematic errors are eliminated. One thing to keep in mind is the calibration of the measuring tape. Just like any ruler, it can be subject to calibration errors.
For most falling objects in air, the air resistance will affect is acceleration. Air resistance is considered a random error because wind-speed varies so it is not constant. But because the ball used in this experiment is heavy and will only fall for a short distance, air resistance has little effect on it. Therefore, the ball’s acceleration is effectively g . Dana Lin, AS3 October 2009 2. Uncertainties in the rule r Assuming that the smallest division on the measuring tape is 0.1cm, then the uncertainty would be + 0.1 cm ( + 0.05cm x 2). This should be taken into account when we calculate g using the equation given earlier on.