We assemble a tripod and hang a pendulum made of straw and a rubber cap on it. We choose 30cm as the length of the pendulum. The length of the pendulum is the distance from the hanging point of the straw to the center of the rubber cap (more precisely, the center of gravity of the rubber cap).
Measure the oscillation period of the pendulum with a mobile phone stopwatch. Measure the duration of ten complete oscillations and calculate the oscillation period T=t/10 from it.
The oscillation period of a 30cm long pendulum, measuring the time of ten oscillations :
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