IB Physics HL Internal Assessment Example

The research question is focused and experimentally workable. It identifies both the dependent relationship and the intended use of the result to determine $k$, which gives the investigation a clear purpose and helps keep the later theory and analysis aligned.

The hypothesis oversimplifies the physics: the period depends on moment of inertia, not just mass, and the effect of added masses also depends on where they are placed relative to the axis. The student should state the relationship in terms of $I$ and explain how changing radius would affect the prediction.

This explanation treats the length as a control variable, but it does not explain why the chosen length is sufficient or how much variation would matter. The student should link each control directly to validity: for example, changing wire length alters $k$, so it must be measured and held fixed to avoid systematic error.

The independent variable would be stronger if it were defined more precisely as the mass configuration or moment of inertia of the system, not only total added mass. Naming the actual controllable quantity would make the design more physically accurate and easier to reproduce.

This control would be stronger if it specified how the position was standardised, such as marking the stand location and fixing the light gate at a measured distance and height. Concrete setup details improve reproducibility and reduce ambiguity.

This is an important methodological issue, but it is stated too generally. The student should identify exactly which positions matter, especially the radius of each added mass from the axis, because that directly changes $I$ and therefore the period.

This conflicts with the later tables, which appear to show only one time value for each mass. The student should make the repeat structure explicit: how many trials were taken per mass, what was averaged, and whether the ten oscillations were timed as one run or ten separate runs.

The method is not reproducible enough here because the student does not explain how the paper flag size, placement, or orientation affects timing. The light gate setup should be described precisely so another investigator could recreate the same trigger conditions.

What radius was each added mass placed at, and was that radius kept constant across all seven configurations? Since rotational inertia depends strongly on radius, answering this would clarify whether the investigation is measuring mass alone or a more controlled change in $I$.

This step leaves too much uncertainty about how a period was obtained from the sensor reading. The student should explain whether one blockade equals half a cycle or a full cycle, and how the raw timing output was converted into one period measurement.

The recorded values in this column are later treated as periods, so the communication is internally inconsistent. The student should label the measured quantity unambiguously and then use that same quantity throughout the processing to avoid confusion and calculation errors.

The student includes a clear raw-data table and follows it with processed tables and graphs, which gives the reader a traceable path from measurement to conclusion. That structure is valuable because it allows the processing choices to be checked against the original recordings.

This is a conceptual mistake: the expression is for a mass-spring system and cannot simply replace $m$ with rotational inertia without changing the structure of the model. The student should use the torsion-pendulum relationship $T=2\pi \sqrt{I/k}$ and define $I$ consistently.

This processed value appears to come from squaring the 6.315 s time entry, but the table labels it as a period. The student should show the conversion step from raw timing to period before any squaring, otherwise the processing chain is not transparent.

The gradient is reported, but the analysis does not demonstrate that the fitted variable on the horizontal axis is actually the quantity needed to determine $k$. The student should make the graph, axis choice, and algebraic rearrangement fully consistent so the gradient leads validly to the final constant.

The processed table is useful in principle, but the uncertainty columns are not clearly defined enough to verify the calculations. The student should state exactly what each uncertainty represents and how each value was propagated into $T^2$ and the final torsional constant.

The units here are only part of the issue: the analysis needs to show whether the plotted horizontal variable is mass, total mass, or moment of inertia. Without that clarity, the slope cannot be interpreted reliably.

This processed result is not interpreted clearly, so the reader cannot tell how it contributes to the determination of $k$. The student should state what $Am$ represents physically and how it is used in the final calculation.

The slope is reported, but the uncertainty and units are not communicated cleanly. The student should present the gradient with correctly formatted units and explain how the uncertainty from the fit feeds into the uncertainty in the torsional constant.

What do these minimum and maximum values actually measure, and are they meaningful as uncertainty bounds when they come from different mass settings? The student should check whether the range is being used correctly before carrying it into later uncertainty work.

This value is not clearly justified from the surrounding table, and it is not obvious why the uncertainty is so large relative to the corresponding period value. The student should show the calculation rule used here so the reader can check whether the uncertainty is reasonable.

The uncertainty calculation is not appropriate here because the spread in values comes from different masses, not repeated measurements of one fixed condition. The student should instead use repetition-based uncertainty for each configuration or justify another valid propagation method.

Does a low percentage uncertainty in one fitted parameter alone justify calling the whole experiment reliable? The student should think about whether conceptual errors in the processed quantities could still make the result inaccurate even when a fit appears precise.

This wording overstates the strength of the evidence. The student should use more cautious language unless the analysis clearly demonstrates statistical or uncertainty-based confirmation.

The conclusion does answer the research question directly and connects the trend to the underlying torsional-pendulum model. That helps the reader see the link between the experimental pattern and the intended physical interpretation.

If the added masses were moved to different radii, can the conclusion still claim proportionality with mass alone? The student should consider whether the evidence actually supports a relationship with total moment of inertia instead.

The student does well to acknowledge limitations in the conclusion rather than presenting the result as perfect. This shows awareness that experimental data should be interpreted in light of real-world effects and not only in terms of the ideal model.

This conclusion is not fully consistent with the analysis because it treats mass as the controlling variable rather than moment of inertia. The student should revise the conclusion to reflect the actual physical dependence, especially if the added masses were placed at different radii.

The conclusion would be stronger if it ended with a concise comparison to the accepted torsion-pendulum relationship, explicitly stating whether the result agrees with $T=2\pi \sqrt{I/k}$ and what the main source of disagreement was.

The claim that the error margins were within limits is not convincingly supported by the analysis, especially given the reported discrepancy between theoretical and experimental $k$. The student should tie the conclusion to the actual uncertainty treatment rather than relying on a general statement of acceptability.

This judgement is asserted rather than justified. The student should explain why damping was small enough not to change the conclusion, ideally by referring back to the size of the observed deviation or uncertainty estimates.

The evaluation section would improve if each weakness were paired with a specific corrective action and a note on its impact. For example, the student could rank the limitations by importance, then explain which ones are most likely to shift $k$ systematically.

This statement is directionally correct but still imprecise, because the problem is not only the added mass but the radius at which it acts. The student should use the actual relationship for rotational inertia to explain why radius creates a much larger effect than a small mass uncertainty.

This is a strong limitation, but the discussion stops short of evaluating its size. The student should explain how a plausible change in radius would alter $I$ so that the reader can judge whether this is the dominant source of error.

The evaluation starts well by identifying a real source of error that is directly relevant to the investigation. Recognising the effect of changing moment of inertia shows that the student understands which aspect of the method most strongly affects validity.

Consider adding a short comparative judgement here: which uncertainty was largest, which was smallest, and why? That would turn a list of limitations into a more analytical evaluation.

This limitation is relevant, but the impact is not explained clearly. The student should state whether damping would bias the period high or low and why that matters for the final torsional constant.

This is another useful limitation, but it remains generic. The student should explain whether varying the initial angle changes the period, the amplitude, or both, and then connect that effect to the reliability of the data.

A stronger improvement would be to propose a measurable fix, such as using an angle marker and a repeatable release jig. That would directly address the limitation and make the method more reproducible.

The student lists instrument uncertainties, but does not explain which ones matter most or how they affect the final value of $k$. The evaluation should distinguish between minor measurement noise and uncertainties that create meaningful systematic error in the calculation.