2022 IB Diploma Extended Essays

- How it was measured: A ruler with increments of 1mm (0.0001m) was taped to the outermost edge of the beaker during the rotations. A phone was used to film the rotations in slow motion for the heights to be determined. - Estimated uncertainty: ± 1mm (±0.0001m) - Number of trials: 5 Controlled: Variable How it was controlled Effect on results The dial determining speed

All trials for the 5 periods were performed without adjustment of the dial. Therefore, the position of the dial did not require repositioning between the trials. The different speeds according to the dial were estimated, although it does not pose a large issue as the speed was not determined through use of the dial. An aliquot of coloured milk was used, to determine the change in heights of the displacement more accurately. 20 ml of the (already coloured) milk was measured using a measuring cylinder with an uncertainty of ±0.5ml and then transferred to the beaker. The same beaker was used and secured to the edge of the apparatus. The radius was measured with a ruler where the smallest increment was 1 mm (0.001m). This ensures that the radius remained the same throughout the experiment. A phone secured with a retort stand was used to secure the phone. The same retort stand was used without adjustment throughout the experiment to ensure the same camera angle.

The uncertainties of the speeds would be very large if there were to be adjustment or recreation of the position of the dial. This would be due to the dial changing the speed at which the apparatus rotates and therefore, the time that 5 rotations would take. The results would have been affected if the amount of each aliquot was different. This is because the faster speeds caused the bottom of the beaker to become exposed, where it would not be if there were more liquid. If the radius had varied throughout the experiment, the circumference would have varied and therefore, changed the speed calculated

Aliquot used

Radius (and therefore, circumference)

Angle of camera

If the camera angle were to vary, the change in height may appear different and therefore, be recorded incorrectly.

3.2.2 Equipment

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