How does the horizontal separation d between two suspension points (varied from 0 mm to 560 mm in steps of 70 mm) affect the period T of oscillation of a block suspended by a rope of fixed length L= 300mm?SL
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7
Official IB Result
20/24
Criteria A: Research Design
5/6
0
3
6
Criteria StrandsPro
A.1Research question context
Excellent
A.2Methodological considerations for collecting data
Moderate
A.3Methodological considerations
Good
Criteria Feedback
- The student frames the investigation with a focused, measurable research question and a clear variable structure.
- The student gives strong contextual motivation that connects the investigation to a real physical application.
- The student shows thoughtful planning by using repeated trials and a timing method designed to reduce random error.
- The student does not fully explain how the swing plane is controlled, which affects reproducibility and validity.
- The student's effective-length model does not fully address the fact that the relevant distance should be measured to the centre of mass.
- Some key methodological conditions are identified but not explained in enough detail to show why they are essential.
1.1·Strength
Page 2
The research question is focused, measurable, and operationally defined. The independent variable, dependent variable, range, step size, and fixed rope length are all stated, so the investigation has a clear experimental structure.
1.2·Strength
Page 2
The context is specific and purposeful, linking the question to slings, cradles, chandelier mounts, and resonance. This makes the research question feel authentic rather than isolated, which is exactly what strong research design should do.
1.3·Suggestion
Page 2
The amplitude argument is well chosen; it would be even stronger if the student briefly linked this calculation to the later uncertainty budget. That would show not just that the small-angle condition is valid, but also why it is negligible relative to the dominant timing uncertainty.
1.4·Strength
Page 2
The student grounds the investigation in the correct physical principle from the outset: period depends on the distance to the centre of mass. This shows strong conceptual framing and helps justify why changing hook separation should affect the motion.
1.5·Weakness
Page 3
This description is ambiguous about the actual swing geometry. It does not state that the block must oscillate in the vertical plane perpendicular to the line joining the hooks, which is essential for the model to be valid and for another student to reproduce the setup correctly.
1.6·Strength
Page 4
The method shows good thought about repeatability and practicality. Using five trials at each separation and timing ten oscillations both improve reliability and reduce the proportional effect of reaction-time error.
1.7·Weakness
Page 4
The student identifies that the attachment point stays fixed, but does not explain how the block’s centre of mass is located relative to that bolt. Without that, the controlled-variable statement is incomplete for a simple-pendulum model.
1.8·Weakness
Page 4
The procedure measures to the block bolt, but the theory for a pendulum requires the distance to the centre of mass. That missing geometric reference weakens the validity of the whole design, especially when the effective lengths become short.
1.9·Strength
Page 5
This step is precise enough to reproduce and shows awareness of how to standardise the release. The student also defines the timing reference point clearly, which helps make the procedure reproducible.
1.10·Question
Page 5
What evidence shows that the swing actually stays in the intended plane during each trial? The student should think about whether a plumb line alone is enough to control the geometry, or whether an additional constraint or alignment check is needed.
Criteria B: Data Analysis
5/6
0
3
6
Criteria StrandsPro
B.1Communication of data recording and processing
Excellent
B.2Consideration of uncertainties
Good
B.3Data processing quality
Moderate
Criteria Feedback
- The student's raw and processed data are presented clearly, with a logical progression from measurements to derived quantities.
- The student treats uncertainty seriously by propagating timing and length uncertainties through the analysis.
- The student's graphs and tables are well labelled and make the trend easy to follow.
- The student's uncertainty treatment does not fully separate random scatter from the uncertainty in the mean.
- The analysis misses the more important model uncertainty linked to the centre of mass position.
- Some uncertainty commentary is inconsistent with the numerical results at the largest separations.
2.1·Strength
Page 5
The raw-data description is clear and complete: it states what was measured, how many trials were taken, and at which variable values. This makes the processing trail easy to follow.
2.2·Weakness
Page 6
The uncertainty treatment is not fully rigorous here because repeated trials are averaged, yet the uncertainty in the mean is not clearly separated from the uncertainty of a single reading. The student should distinguish random scatter, reaction-time error, and uncertainty in the mean so the propagation is conceptually sound.
2.3·Suggestion
Page 6
A brief line showing the full calculation chain from to , , and would make the processing easier to audit. That would help a reader verify each propagated uncertainty step without having to infer intermediate values.
2.4·Weakness
Page 6
This systematic estimate is presented clearly, but it is based only on rope-length uncertainty. It misses the larger validity issue that the model uses the bolt position instead of the centre of mass, so the most important uncertainty source is not being considered.
2.5·Strength
Page 7
The processed-data table is well structured and communicates the transformations clearly. Including both absolute and percentage uncertainties lets the reader judge how uncertainty grows across the range.
2.6·Weakness
Page 7
The processed data show that uncertainty grows substantially at the largest separation, yet the discussion still later treats the rope-length contribution as negligible. The student should reconcile this with the table, where the percentage uncertainty becomes much larger at mm.
2.7·Strength
Page 8
The graph annotation is precise and scientifically useful because it states exactly how uncertainty is represented visually. That supports the interpretation of the trend and shows careful communication of measurement quality.
2.8·Strength
Page 9
The student clearly identifies the regression line and distinguishes it from the theoretical and limiting lines. This makes the graph readable and shows a good understanding of how the processed data are being analysed.
2.9·Question
Page 14
If timing error were reduced so much, would rope-length uncertainty still be the main limitation, or would the centre-of-mass model error become more important first? The student should consider which source would dominate once the stopwatch error is removed.
Criteria C: Conclusion
4/6
0
3
6
Criteria StrandsPro
C.1Conclusion relevance and support
Moderate
C.2Scientific context comparison
Good
Criteria Feedback
- The student states a clear conclusion that directly answers the research question.
- The student supports the conclusion with numerical evidence from the data and compares their result with accepted values using uncertainty intervals.
- The student shows some scientific judgement by avoiding an overconfident claim of precision.
- The student's conclusion depends on a model assumption that is not fully justified earlier in the investigation.
- The explanation is not completely consistent with the geometric limitations of the setup.
- The comparison to scientific context is useful, but it would be stronger if the assumptions behind that comparison were made explicit.
3.1·Strength
Page 10
The conclusion answers the research question directly and uses specific numerical evidence from the data. The student also links the trend back to the model, which shows strong continuity between analysis and conclusion.
3.2·Strength
Page 10
The comparison with accepted values is handled appropriately because it uses the uncertainty interval rather than only the central value. This shows good scientific judgement and prevents overclaiming precision.
3.3·Question
Page 10
Does this conclusion fully follow from the model used in the investigation, or does it partly depend on an assumption about where the effective pendulum length is measured from? The student should check that the stated explanation matches the physical setup, not just the data trend.
3.4·Suggestion
Page 10
The comparison to both standard and local values is a strong move; it would be even better if the student briefly explained why the local value is appropriate as a secondary comparison and what assumptions allow a laboratory pendulum experiment to compare with geodetic measurements.
3.5·Weakness
Page 10
The practical application is interesting, but it is built on the same incomplete pendulum model. Because the analysis does not fully justify the effective length definition, the resonance claim should be treated as tentative rather than as a firm design recommendation.
Criteria D: Evaluation
6/6
0
3
6
Criteria StrandsPro
D.1Methodological weaknesses
Excellent
D.2Suggested improvements
Excellent
Criteria Feedback
- The student identifies specific limitations rather than listing generic weaknesses.
- The student explains how the main limitations affect the result, especially the influence of manual timing on uncertainty.
- The student proposes realistic improvements that are directly linked to the problems they identified.
- The evaluation does not prioritise the most fundamental validity issues strongly enough.
- Some limitations would be more convincing if the student quantified their likely impact more explicitly.
- The student's improvements would be stronger if they addressed the geometry and centre-of-mass issue first.
4.1·Weakness
Page 10
The ranking is useful, but it is incomplete because the most serious validity issue is not included: the model uses the bolt rather than the centre of mass, and the swing plane is not explicitly controlled. The student should prioritise limitations by impact on validity, not only by calculated uncertainty.
4.2·Strength
Page 10
The limitation is not just named but linked to its effect on the final result. Explaining that manual timing drives the gradient uncertainty makes the evaluation far more analytical than a generic list of weaknesses.
4.3·Suggestion
Page 10
This is a strong improvement, and it would be even more convincing if the student added how the timing protocol would change when the bob passes the gate. For example, specifying the counting logic or software output would make the method more reproducible.
4.4·Strength
Page 11
This improvement is realistic, specific, and directly tied to the limitation it addresses. The student does not merely say to 'improve angle control' but gives an implementable method that would actually reduce uncertainty.
4.5·Weakness
Page 11
This is a thoughtful limitation, but the explanation would be stronger if it quantified how large such a bias could realistically be. Without a magnitude estimate, it is harder to compare this effect with the stopwatch uncertainty and judge its relative importance.
4.6·Strength
Page 11
The student explains why the proposed change would help, not just what to change. That cause-and-effect reasoning is exactly what makes an evaluation convincing and criterion-appropriate.
4.7·Weakness
Page 14
The improvement is realistic, but the evaluation underestimates what would matter next. Once timing is improved, the investigation would still need to address the centre-of-mass/bolt mismatch and the oscillation plane, which are more fundamental than rope-length precision.