Physical quantities and measurement techniques — Determine

How can you find an accurate value for a small distance or short time interval, such as the period of a pendulum?

Measure a number of repeats together and divide by that number: for example, time 20 complete oscillations of a pendulum with a stopwatch, then divide by 20 to find the period. This reduces the percentage effect of reaction-time error compared with timing a single oscillation. The same multiple-measurement method can be used for a small distance, e.g. measuring the thickness of many identical sheets stacked together and dividing by the number of sheets.