What the investigation does
The student varies the draw length of a recurve bow and compares the work put into the bow with the kinetic energy transferred to an arrow. Force readings are fitted and integrated to estimate stored energy, while high-speed video and motion-analysis software estimate arrow speed.
Efficiency is calculated as arrow kinetic energy divided by input work. The paper reports a rise and then a fall in efficiency, with a fitted peak near 52 cm, and discusses release technique, variable draw length, blurred video tracking and outdoor conditions as limitations of the experiment.
Why this example is worth reading
The research question connects a measurable mechanical property with a clear energy-transfer calculation and goes beyond assuming Hooke's law.
The method combines two forms of evidence, force-displacement measurements and video-derived speed, to construct the efficiency result.
The evaluation links human release technique and image-tracking choices to specific effects on measured arrow speed and the efficiency calculation.
What the examiner highlights
The examiner praises the focused topic, accessible technology and extension beyond Hooke's law, while noting that the experiment was conducted safely at an archery club.
The commentary calls for fuller speed-measurement detail, a better release mechanism, deeper treatment of recurve-bow physics and more consistent uncertainties and terminology.
The examiner recommends moving essential sample data and diagrams from the appendix into the main argument and comparing work and kinetic energy on one graph.
What to examine critically
The examiner identifies incomplete explanation of video-based speed measurement, inconsistent uncertainties and significant figures. Reproduce the measurement chain and uncertainty propagation before accepting the numerical optimum.
The reported peak is tied to this bow, release method and fitted data. It should not be treated as a general recommendation for bow setup or as a well-established optimum outside the sampled range.
Apply it to your own work
Define efficiency operationally and show how each measured quantity enters its calculation.
Separate uncertainty in measurement from limitations of the fitted model.
Place the evidence needed to follow the reasoning in the main essay.
Essay & assessment material
Read the original material alongside the breakdown, or download it to keep.
A separate one-page examiner commentary accompanies the essay. It describes achievement at the low end of the top range without providing a numeric mark or individual letter grade.
Source & assessment context
50 More Excellent Extended Essays (IB, 2011). The source PDFs retain their original attribution. The analysis on this page is AsterDraft’s independent teaching commentary.
Examiner-described top-range achievement; numeric mark not stated. A separate one-page examiner commentary accompanies the essay. It describes achievement at the low end of the top range without providing a numeric mark or individual letter grade.