Determining period and frequency from simple harmonic motion

The 2 pictures show a simple penduluym and a amss attached to a spring. The number of oscillations is timed using a stop watch and this can show the period is indepenent of the amplitude.

The time taken for several complete oscillations is measured, the process is repeated and the period calculated from the average time.

A small pin is placed at the equilibrium position. This fiducial marker provides a clear point from which to start and stop timing the oscillations.

Why should a marker be placed at the quilibrium position?

At the equilibrium, the object is moving at its highest speed (highest KE), so the marker reduces uncertainty in the timing measurements. The object will always move through its equilibrium position, even if the motion is damped

Explain why you would record several oscillations, rather than a single swing.

The effect of random errors is reduced and also reduces uncertainty in the measured time due to human errors e.g. reaction time