📚 AS Physics PH01 June 2022 Exam Report: Experimental Investigation Analysis | AS 物理 PH01 2022年6月考试报告：实验探究分析
The PH01 June 2022 examiners' report offers valuable insights into how students tackled the experimental investigation component. This article distils the key findings, common pitfalls, and best practices observed in the assessment of practical skills. By understanding the examiner's perspective, learners can refine their approach to data collection, error analysis, and graph plotting to achieve higher marks in AS Physics.
2022年6月PH01考试报告深入剖析了学生在实验探究题中的表现。本文提炼了评估实践技能时发现的关键要点、常见错误和优秀做法。透过考官的视角，学生可以优化数据收集、误差分析和绘图方法，从而在AS物理考试中取得更好成绩。
1. Experiment Overview: Determination of g via Free Fall | 实验概述：通过自由落体测定重力加速度 g
The core task in this investigation was to measure the acceleration due to gravity, g, by studying the motion of a freely falling object. A small steel sphere was released from an electromagnet and the time taken to fall through a measured distance was recorded electronically.
本次探究的核心任务是通过研究自由落体运动来测量重力加速度 g。实验中，一个小钢球从电磁铁释放，电子计时器记录其下落通过一定距离所用的时间。
½ g t². By measuring s and t, students could derive g from a suitable graphical analysis.
距离 s 与时间 t 的关系可由静止开始的匀加速运动学方程给出：s = ½ g t²。通过测量 s 和 t，学生可以利用图像分析求出 g。
2. Equipment and Setup | 仪器与装置
The standard apparatus included an electromagnet connected to a low-voltage DC supply, a steel sphere, a vertical metre rule, a trapdoor or light-gate sensor, and an electronic timer. Some schools used two light gates to eliminate uncertainties associated with the release mechanism.
标准装置包括连接低压直流电源的电磁铁、钢球、竖直米尺、活板门或光电门传感器，以及电子计时器。部分学校使用双光电门来消除释放机构带来的不确定性。
A crucial detail emphasized in the report was the importance of aligning the metre rule vertically and ensuring the sphere fell directly through the sensing zone. Any misalignment introduced parallax errors and unreliable timing.
报告中强调的一个关键细节是米尺必须垂直对齐，并确保小球下落路径直接穿过感应区域。任何未对准都会引入视差误差并导致计时不可靠。
3. Procedure Step-by-Step | 操作步骤
The procedure involved setting the distance s from the bottom of the sphere to the sensing point, then switching off the electromagnet to release the sphere. The timer started when the circuit was broken and stopped when the sphere interrupted the light gate or hit the trapdoor.
操作步骤包括设定小球底部到感应点的距离 s，然后断开电磁铁电源释放小球。电路断开的瞬间计时器开始计时，小球遮挡光电门或撞击活板门时计时停止。
Multiple readings were required for each value of s to calculate a mean time t. The report noted that many candidates only took two readings for each s, which did not provide a reliable average and often led to inconsistent plots.
每个 s 值需多次读数以计算平均时间 t。报告指出，许多考生对每个 s 只取两次读数，无法提供可靠的平均值，往往导致图上数据点不一致。
The range of distances used was usually from 0.20 m to 1.00 m in steps of 0.10 m. The report praised students who included a wide range of s, allowing better gradient determination.
所选距离范围通常为 0.20 m 至 1.00 m，步长 0.10 m。报告赞扬那些采用较大 s 范围的学生，因为这样更有利于确定斜率。
4. Data Collection and Recording | 数据收集与记录
Data tables should show repeated time readings, mean time t, and the calculated quantity t². The report highlighted that many candidates omitted units in column headings, a traditional marking pitfall. A correct heading should read 't / s' or 't² / s²'.
数据表应展示重复的时间读数、平均时间 t 和计算量 t²。报告强调许多考生在表头遗漏单位，这是一个历来的失分点。正确的表头应为 't / s' 或 't² / s²'。
Examiners also found rounding errors; some students rounded raw times to one or two significant figures before calculating t², causing distortion in the final graph. Best practice is to keep raw data to the full precision of the timer and only round at the end.
考官还发现有修约错误；一些学生在计算 t² 前便将原始时间修约至一或两位有效数字，导致最终图像失真。最佳做法是保留计时器显示的全部精度，只在最后修约。
The following table illustrates a model data set for this experiment:
下表展示该实验的示例数据集：
| s / m | t₁ / s | t₂ / s | t₃ / s | mean t / s | t² / s² |
|---|---|---|---|---|---|
| 0.200 | 0.203 | 0.199 | 0.201 | 0.201 | 0.0404 |
| 0.400 | 0.286 | 0.287 | 0.285 | 0.286 | 0.0818 |
| 0.600 | 0.352 | 0.350 | 0.351 | 0.351 | 0.123 |
| 0.800 | 0.404 | 0.403 | 0.405 | 0.404 | 0.163 |
| 1.000 | 0.452 | 0.450 | 0.451 | 0.451 | 0.203 |
5. Graphical Analysis Technique | 图像分析技巧
through the origin with gradient k = ½ g. Hence, g can be found by doubling the gradient.
标准方法是绘制 s (纵轴) 对 t² (横轴) 的图像。方程 s = ½ g t² 表明这是一条过原点的直线，斜率 k = ½ g，因此 g 可通过斜率的两倍求得。
Examiners reported that many candidates plotted t² against s instead, leading to a gradient of 2/g and unnecessary algebraic confusion. The report reminded students to label axes clearly with quantity and unit, for example 's / m' and 't² / s²'.
考官反映许多考生误将 t² 对 s 作图，导致斜率为 2/g，带来不必要的代数混乱。报告提醒学生需用物理量和单位清晰标注坐标轴，例如 's / m' 和 't² / s²'。
A further common weakness was choosing an awkward scale that did not spread data points across at least half the graph paper. Students should avoid scales in multiples of 3 or 7, opting instead for 1, 2, 5 or 10 subdivisions per major grid.
另一个常见缺陷是选取不合适的坐标刻度，使数据点未能占据至少一半的图幅。学生应避免使用 3 或 7 的倍数作为刻度，而选择每大格 1、2、5 或 10 的划分。
The derived gradient should be shown on the graph with a large triangle, and its value used to calculate g. The report stressed that reading values from the best-fit line, not from data points, is essential for accuracy.
计算斜率时应在图上画出大三角形，并用斜率值求 g。报告强调必须从最佳拟合线上取值，而非原始数据点，才能保证准确性。
6. Common Mistakes Identified in the Exam | 考试中发现的常见错误
One prevalent mistake was assuming the electromagnet released the sphere instantaneously. In reality, residual magnetism can delay the release, causing the measured time to be shorter than the true free-fall time.
一个普遍错误是假定电磁铁能瞬间释放小球。实际上，剩磁会延迟释放，导致测得的时间短于真正的自由落体时间。
Many candidates failed to account for the finite diameter of the sphere when setting the distance s. The distance should be measured from the bottom of the sphere to the sensing point, not from the centre, to avoid a systematic error.
许多考生在设定距离 s 时未考虑小球的直径。距离应从球底量至感应点，而非球心，以避免系统误差。
The report also noted that some students ignored air resistance, particularly for larger distances, leading to overestimation of g if they assumed ideal free fall. Examiner comments suggested that this was a weak point in theoretical discussion.
报告还注意到部分学生忽略空气阻力的影响，尤其是下落距离较大时，若假定理想自由落体，会导致 g 被高估。考官评语指出这是理论讨论中的薄弱环节。
7. Understanding and Reducing Uncertainties | 理解和减小误差
t digit on the timer, unless there is a reaction-time element. In the electromagnetic release experiment, the main uncertainty is often random scatter due to the release mechanism.
对于单次时间测量，不确定度通常为计时器最小位读数的 ± 值，除非涉及反应时间。在电磁释放实验中，主要不确定度常源于释放机构导致的随机离散。
Examiners encouraged students to calculate the percentage difference between repeated trials and, where appropriate, estimate the uncertainty in t² by using the range of t values. They also reminded candidates that the absolute uncertainty in t² is approximately 2t Δt.
考官鼓励学生计算重复试验间的百分差，并适当地利用 t 值的极差来估计 t² 的不确定度。他们还提醒考生，t² 的绝对不确定度约等于 2t Δt。
To reduce timing uncertainty, using two light gates with a known separation eliminates the electromagnet delay entirely. This improved method was discussed in several high-scoring scripts.
为减小计时不确定度，使用相隔已知距离的双光电门能完全消除电磁铁延迟。这一改进方法在多份高分答卷中被讨论。
8. Examiner's Recommendations for Improvement | 考官的建议与改进措施
The examiners suggested that students practice drawing lines of worst fit to quantify the uncertainty in the gradient. This simple technique involves plotting error bars and drawing the steepest and shallowest possible lines through them.
考官建议学生练习绘制最佳拟合线和最差拟合线，以量化斜率的不确定度。这一简单技巧包括画误差棒，并通过它们画出尽可能最陡和最浅的直线。
They also advised writing a clear conclusion that compares the experimental value of g with the accepted value (9.81 m s⁻²), stating the percentage error and commenting on the reliability of the result relative to uncertainties.
他们同时建议写出清晰的结论，将实验测得的 g 值与公认值 (9.81 m s⁻²) 比较，给出百分差，并结合不确定度评价结果的可靠性。
The report underlined that simply stating 'human error' or 'parallax error' without specific context gained no credit. Candidates must pinpoint exactly how the error affects the measurement and suggest a practical refinement, such as using a plumb line for alignment.
报告强调，笼统地写 '人为误差' 或 '视差' 而不给出具体情境无法得分。考生必须准确说明该误差如何影响测量，并提出实际改进措施，例如使用铅垂线校准。
9. Applying the Skills to Other Investigations | 将这些技能应用于其他实验探究
The methodology of measuring a time interval for a known distance to determine an acceleration underpins many AS experiments, such as investigating the motion of a trolley down an incline or measuring g using a simple pendulum.
通过测量已知距离对应的时间间隔来求加速度的方法，是诸多 AS 实验的基础，例如探究小车沿斜面运动的加速度，或用单摆测定 g。
When using a pendulum, the relationship becomes T = 2π √L/g, and a graph of T² against L yields g from the slope. The report noted that candidates who had mastered free-fall graph techniques could transfer those skills seamlessly to the pendulum experiment.
使用单摆时，关系式为 T = 2π √L/g，通过绘制 T² 对 L 的图像可由斜率求出 g。报告指出，掌握了自由落体图像技巧的考生可以顺利将这些技能迁移至单摆实验。
In both cases, reducing uncertainties relies on repeating measurements, using a fiducial marker, and choosing appropriate ranges. The examiners' report therefore serves as a general guide for all AS Physics practical investigations.
无论在哪种实验，减小不确定度都依赖于重复测量、使用定位标记和选择合适的范围。因此，这份考官报告可作为所有 AS 物理实验探究的通用指南。
10. Conclusion: Key Takeaways for AS Physics Students | 结语：AS 物理学生的关键要点
The June 2022 PH01 report confirms that success in experimental investigations demands meticulous attention to detail: correct table headings, appropriate significant figures, well-planned graphs, and rigorous error analysis. Re-reading the assessment criteria through the lens of these examiner comments can significantly boost confidence and performance.
2022年6月PH01报告证实，在实验探究中取得成功需要一丝不苟地关注细节：正确的表头、合适的有效数字、精心设计的图像和严谨的误差分析。透过这些考官评语重温评分标准，可以显著提升信心和表现。
Remember that the heart of practical physics is not just following a list of instructions, but constantly asking why a particular method reduces uncertainty and how the experiment could be made more accurate. The best candidates demonstrated this reflective mindset.
请记住，实验物理的核心并非只是按步骤操作，而是不断思考某种方法为何能减小不确定度，以及如何使实验更为精确。最优秀的考生展现了这种反思性思维。
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