Experimental Investigation in AS Physics | 国际物理AS实验探究

📚 Experimental Investigation in AS Physics | 国际物理AS实验探究

In AS-level physics, the experimental investigation is a crucial component that tests your ability to plan, carry out, analyse, and evaluate a practical task. You are expected to handle apparatus with confidence, record data with precision, process uncertainties, and draw scientifically sound conclusions. This article walks you through the key stages of a typical physics investigation, with paired English-Chinese explanations to reinforce both subject knowledge and bilingual academic literacy.

在国际AS物理课程中，实验探究是对你规划、实施、分析和评估实验能力的核心考查。你需要熟练操作仪器、精确记录数据、处理不确定度，并得出合理的科学结论。本文将带你走完典型物理实验的关键步骤，每部分都配有中英双语解析，帮助巩固学科知识与双语学术表达。

1. Understanding the Aim | 明确实验目标

The aim states what you are trying to find out, often expressed as a relationship between two physical quantities. For example: “To determine the acceleration due to gravity, g, using a simple pendulum.” A clear aim ensures you design a focused procedure.

实验目标说明你想要探究什么，通常表达为两个物理量之间的关系。例如：“使用单摆测定重力加速度g。”清晰的目标能确保实验设计方向明确。

2. Identifying Variables | 识别变量

Independent variable – the quantity you deliberately change (e.g., length of pendulum). Dependent variable – the quantity you measure (e.g., period T). Control variables – quantities kept constant to ensure a fair test (e.g., amplitude of swing, mass of bob).

自变量——你主动改变的量（如摆长）。因变量——你测量的量（如周期T）。控制变量——为公平实验而保持不变的量（如摆动振幅、摆球质量）。

3. Apparatus and Setup | 实验器材与装置

List all equipment with sensitivity or precision where relevant: metre rule (±1 mm), digital stopwatch (±0.01 s), clamp stand, protractor, etc. A clearly labelled diagram helps communicate the setup. Mention how you reduce parallax and ensure alignment.

列出所有器材并注明灵敏度或精度：米尺（±1 mm）、数字秒表（±0.01 s）、铁架台、量角器等。清晰的标注图示有助于表达实验装置。说明如何减少视差并确保对准。

4. Risk Assessment | 风险评估

Identify hazards and precautions. For the pendulum: clamp stand may topple – place a counterweight; bob could swing into someone – keep clear zone; avoid large amplitudes to maintain simple harmonic motion. Always tie back loose clothing and hair.

识别危险源及预防措施。单摆实验：铁架台可能倾倒——放置配重；摆球可能打到人——保持安全区域；避免大振幅以维持简谐运动。务必束好宽松衣物和头发。

5. Method and Data Collection | 实验方法与数据收集

Describe the step-by-step procedure. E.g., set pendulum length L = 1.000 m, displace by less than 10°, release and time 20 complete oscillations (t₂₀). Repeat twice for each L and calculate mean period T = t₂₀/20. Vary L in 10 cm steps from 0.100 m to 1.000 m. Record raw readings in a table immediately.

描述逐步操作步骤。例如：设置摆长 L = 1.000 m，偏离小于10°，释放并计时20次完整摆动的时间t₂₀。每个L重复两次，计算平均周期 T = t₂₀/20。将L以10 cm为步长从0.100 m变化到1.000 m。立即在表格中记录原始读数。

6. Table of Results | 数据记录表

Design a table with clear headings and units. Include columns for raw data, processed data (mean time, period T, T²), and absolute uncertainties. Record all values to appropriate significant figures, consistent with instrument precision.

设计表格，清晰的标题和单位。包括原始数据、处理数据（平均时间、周期T、T²）以及绝对不确定度的列。所有数值按适当的有效数字记录，与仪器精度一致。

L / m	t₂₀ / s (trial 1)	t₂₀ / s (trial 2)	Mean t₂₀ / s	T / s	T² / s²
0.200	18.05	18.12	18.09	0.905	0.819

Remember to calculate and include the instrumental uncertainty for each column, e.g., stopwatch reading uncertainty ±0.01 s, reaction time ~0.1 s. The larger uncertainty should be used.

记住计算并注明每列仪器不确定度，例如秒表读数不确定度±0.01 s，反应时间~0.1 s，应使用较大值。

7. Graphical Analysis | 图形分析

Plot a graph of T² (y-axis) against L (x-axis). Use a sharp pencil, label axes with quantity/unit, choose sensible scales occupying >half the grid, and draw error bars if appropriate. According to T = 2π√(L/g), T² = (4π²/g)L, so a straight line through origin is expected.

绘制T²（纵轴）随L（横轴）变化的图。用锋利的铅笔、标注物理量/单位、选择合理的比例尺占据过半网格，必要时画误差棒。根据T = 2π√(L/g)，T² = (4π²/g)L，因此预期为一条过原点的直线。

8. Gradient and Uncertainty | 斜率与不确定度

Draw best-fit line and worst-fit line (or use extreme points) to determine gradient m. m = Δ(T²)/ΔL. The uncertainty in gradient Δm = |m_best – m_worst|. From m = 4π²/g, calculate g = 4π²/m. Propagate uncertainty: Δg/g = Δm/m.

作出最佳拟合线和最差拟合线（或使用极值点）求斜率 m = Δ(T²)/ΔL。斜率的不确定度 Δm = |m_best – m_worst|。由 m = 4π²/g，计算 g = 4π²/m，并传递不确定度：Δg/g = Δm/m。

9. Calculating Derived Quantities | 计算导出量

Numerical example: if m = 4.00 s²/m, then g = 4π²/4.00 ≈ 9.87 m/s². If Δm = 0.05 s²/m, percentage uncertainty in g = (0.05/4.00)×100% = 1.25%, so absolute Δg = 0.0125 × 9.87 ≈ 0.12 m/s². Hence g = 9.87 ± 0.12 m/s².

数值例子：若 m = 4.00 s²/m，则 g = 4π²/4.00 ≈ 9.87 m/s²。若 Δm = 0.05 s²/m，g的百分不确定度 = (0.05/4.00)×100% = 1.25%，因此绝对 Δg = 0.0125 × 9.87 ≈ 0.12 m/s²。所以 g = 9.87 ± 0.12 m/s²。

10. Drawing Conclusions | 得出结论

Compare your experimental value with the accepted value (e.g., 9.81 m/s²). State whether they agree within experimental uncertainty. Discuss the linearity and whether the graph passes through origin – a y-intercept significantly non-zero might indicate systematic error.

将实验值与公认值（如9.81 m/s²）比较。说明在实验误差范围内是否吻合。讨论线性关系及图线是否过原点——显著的y轴截距可能暗示系统误差。

11. Evaluation and Improvements | 评估与改进

Identify the main sources of uncertainty: reaction time in starting/stopping stopwatch, measurement of L using metre rule, difficulty in keeping small amplitude. Suggest improvements: use light gates to time oscillations, measure L from pivot to centre of bob more precisely, use a fiducial marker at equilibrium to improve timing consistency. Explain how each improvement reduces uncertainty.

识别主要的不确定度来源：秒表启动/停止时的反应时间、用米尺测量L的误差、保持小振幅的困难。提出改进：使用光门计时、更精确地测量从悬挂点到摆球中心的L、在平衡位置设置基准标记以提高计时一致性。解释每个改进如何降低不确定度。

12. Common Pitfalls | 常见误区

Many students forget to convert units, misplot T instead of T², neglect to repeat readings, or treat reaction time as negligible. Always check if the graph’s form matches the theoretical prediction. Practice writing the conclusion linking gradient to physical constants, and quote uncertainty with the correct number of significant figures.

很多学生忘记单位转换，错误地描绘T而非T²，忽略重复读数，或错误地认为反应时间可忽略。务必检查图像形式是否符合理论预测。练习书写将斜率与物理常数联系起来的结论，并用正确的有效数字位数注明不确定度。

Published by TutorHao | Physics Revision Series | aleveler.com

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