AP Physics 1: Free-Response Questions (FRQ) Analysis | AP 物理1：真题（FR）解析

📚 AP Physics 1: Free-Response Questions (FRQ) Analysis | AP 物理1：真题（FR）解析

AP Physics 1 free-response questions challenge students to apply conceptual understanding, mathematical reasoning, and experimental design skills. This article breaks down typical FRQ types, common pitfalls, and effective strategies to help you score high.

AP 物理1自由回答题考察学生对概念理解、数学推理和实验设计技能的综合运用。本文剖析典型FRQ题型、常见陷阱和高效得分策略，助你斩获高分。

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1. Overview of AP Physics 1 FRQs | AP 物理1 FRQ 概览

The AP Physics 1 exam includes 5 FRQs to be completed in 90 minutes. One question focuses on experimental design, one is a Qualitative-Quantitative Translation (QQT), and the remaining three are short-answer questions covering multiple topics.

AP物理1考试包含5道简答题，需在90分钟内完成。其中一道为实验设计题，一道为定性定量转换题（QQT），其余三道为覆盖多个主题的短答案题。

Each FRQ is scored on a rubric that awards points for correct physics principles, proper use of equations, logical reasoning, and clear communication. Partial credit is often given, so showing your work in a structured manner is essential.

每道FRQ根据评分标准给分，正确的物理原理、方程使用、推理逻辑和清晰表达均可得分。常可获得部分分数，因此结构化地展示解题过程至关重要。

The table below summarizes the typical FRQ distribution:

下表总结了典型FRQ题型分布：

FRQ Type 题型	数量	Key Skills 核心技能
Experimental Design 实验设计	1	Design an experiment, identify variables, reduce uncertainty, graphical analysis
Qualitative-Quantitative Translation 定性定量转换	1	Explain physical relationships using both words and equations
Short Answer 短答案题	3	Apply concepts from kinematics, dynamics, energy, momentum, rotation, SHM

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2. Kinematics and Graphical Analysis | 运动学与图像分析

A classic FRQ style presents a position-time or velocity-time graph and asks the student to interpret motion. The slope of a position-time graph gives velocity, while the area under a velocity-time graph yields displacement.

经典FRQ题目会给出位置-时间或速度-时间图像，要求解释运动。位置-时间图的斜率表示速度，速度-时间图下面积表示位移。

For example, if a velocity-time graph shows a horizontal line at v = +5 m/s, the object moves with constant velocity. The displacement after 4 seconds is simply area = (5 m/s)(4 s) = 20 m. If the line slopes downward, acceleration is negative.

例如，若速度-时间图显示一条v = +5 m/s的水平线，物体做匀速运动。4秒后的位移即为面积 = (5 m/s)(4 s) = 20 m。若图线向下倾斜，则加速度为负。

Students often confuse the motion with the shape of the graph. A parabolic position-time graph indicates constant acceleration because the slope (velocity) changes linearly.

学生常将运动与图像形状混淆。抛物线形的位置-时间图说明加速度恒定，因为斜率（速度）线性变化。

When given a multi-segment graph, break the motion into intervals, note the initial conditions, and use kinematic equations cautiously: v = v₀ + aΔt and Δx = v₀Δt + ½ a(Δt)². Always check sign conventions.

遇到多段图像时，将运动分段，标注初始条件，并谨慎使用运动学方程：v = v₀ + aΔt 及 Δx = v₀Δt + ½ a(Δt)²。务必验核正负号规定。

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3. Newton’s Laws and Free-Body Diagrams | 牛顿定律与受力图

Many FRQs require drawing a free-body diagram (FBD) for an object on an incline, connected by a string, or in an elevator. All forces must be labeled clearly: weight (mg), normal (F_N), friction (f), tension (T), etc.

许多FRQ要求为斜面上的物体、用绳子连接的物体或电梯中的物体画受力图。所有力需清晰标注：重力（mg）、法向力（F_N）、摩擦力（f）、拉力（T）等。

On a frictionless incline, the parallel component of weight is mg sinθ, and the perpendicular component is mg cosθ. The normal force balances mg cosθ if no other vertical forces act.

在光滑斜面上，重力沿斜面分量为mg sinθ，垂直斜面分量为mg cosθ。若没有其他竖直方向力，法向力与mg cosθ平衡。

After drawing the FBD, apply Newton’s second law in component form: ΣF_x = ma_x, ΣF_y = ma_y. Choose a coordinate system aligned with the acceleration direction to simplify the equations.

完成受力图后，用分量形式写出牛顿第二定律：ΣF_x = ma_x, ΣF_y = ma_y。将坐标轴方向与加速度方向对齐可简化方程。

A topical FRQ: a block on a rough horizontal table is pulled by a string over a pulley to a hanging mass. The FBD shows tension T acting on both masses, friction fₖ = μₖ F_N opposing motion. Write ΣF = ma for each mass and solve simultaneously to find acceleration or tension.

一道典型FRQ：粗糙桌面上的物块通过滑轮由重物牵引。受力图显示张力T作用在两个物体上，动摩擦力fₖ = μₖ F_N与运动方向相反。分别对每个物体写ΣF = ma并联立求解加速度或拉力。

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4. Conservation of Energy and Work | 能量守恒与功

Energy FRQs typically explore the conversion between gravitational potential energy, kinetic energy, and elastic potential energy. The principle is: when only conservative forces do work, mechanical energy is conserved: ½ mv₁² + mgh₁ = ½ mv₂² + mgh₂.

能量FRQ通常探讨重力势能、动能与弹性势能间的转化。当只有保守力做功时，机械能守恒：½ mv₁² + mgh₁ = ½ mv₂² + mgh₂。

If friction is present, use the work-energy theorem: W_nc = ΔKE + ΔPE, where W_nc is the work done by non-conservative forces (e.g., friction = -f d). Pay careful attention to the sign of work.

若有摩擦力，使用功能定理：W_nc = ΔKE + ΔPE，其中W_nc为非保守力做的功（例如摩擦力做功 = -f d）。务必注意功的正负。

Example: a block slides down a frictionless curved track, then compresses a spring. The initial height h determines the kinetic energy at the bottom: v = √(2gh). That kinetic energy converts entirely into spring potential energy ½ k x_max², giving maximum compression x_max = √(2mgh/k).

例题：滑块从光滑曲面轨道滑下后压缩弹簧。初始高度h决定底部动能：v = √(2gh)。该动能完全转化为弹簧势能½ k x_max²，得到最大压缩量x_max = √(2mgh/k)。

When a problem asks for the speed at an intermediate point, identify which energies have not yet been fully converted. Consistent use of a zero reference for gravitational potential energy is essential.

当题目求中间某点的速度时，要辨别哪些能量尚未完全转化。始终一致地设定重力势能零点至关重要。

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5. Momentum and Collisions | 动量与碰撞

Momentum FRQs often feature collisions or explosions, where the total momentum of an isolated system is conserved: p_initial = p_final. For a two-body system: m₁v₁ᵢ + m₂v₂ᵢ = m₁v₁_f + m₂v₂_f. Remember momentum is a vector; directions matter.

动量FRQ常涉及碰撞或爆炸，孤立系统的总动量守恒：p_initial = p_final。对于两体系统：m₁v₁ᵢ + m₂v₂ᵢ = m₁v₁_f + m₂v₂_f。记住动量是矢量，方向不可忽略。

In perfectly inelastic collisions, objects stick together, and final velocity is found by conservation of momentum alone (kinetic energy is not conserved). In elastic collisions, both momentum and kinetic energy are conserved.

在完全非弹性碰撞中，物体粘在一起，仅用动量守恒即可求末速度（动能不守恒）。弹性碰撞则动量与动能均守恒。

The impulse-momentum theorem J = Δp = F_avg Δt is frequently tested. For instance, a ball bouncing off a wall: the change in velocity reverses direction, so Δp is larger than just mv; thus average force is larger.

常考冲量-动量定理 J = Δp = F_avg Δt。例如球撞击墙壁反弹：速度方向反向，Δp大于仅mv的模，因而平均力更大。

When analyzing a momentum bar chart or a collision graph, carefully assign positive direction and check for external impulses. If a net external force acts during the collision, momentum is not conserved for that system alone.

分析动量柱状图或碰撞图像时，要谨慎设定正方向并检查有无外力冲量。若碰撞过程中存在合外力，则系统动量不守恒。

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6. Rotational Motion and Torque | 转动运动与扭矩

Rotational FRQs require linking linear and angular quantities. For a rolling object, the condition v = ωR ties translational speed v to angular speed ω. Torque τ = r F sinθ causes angular acceleration: Στ = Iα, where I is moment of inertia.

转动FRQ需要联系线量与角量。对于滚动物体，关系式v = ωR将平动速率v与角速率ω联系起来。扭矩τ = r F sinθ产生角加速度：Στ = Iα，其中I为转动惯量。

A common scenario: a beam supported at one end with a hanging mass. To find the tension in a cable, set the net torque about the pivot to zero: torque from weight = torque from tension. Use clockwise/counterclockwise signs consistently.

常见情形：梁一端支承，悬挂重物。求缆绳拉力时，设定绕支点的合扭矩为零：重力矩 = 拉力力矩。始终统一使用顺时针/逆时针正负号。

For a solid sphere rolling down an incline without slipping, conservation of energy must include both translational and rotational kinetic energy: ½ mv² + ½ Iω² = mgh. Substituting I = ⅖ mR² and v = ωR yields a specific acceleration.

对于无滑滚下斜面的实心球，能量守恒须同时包含平动与转动动能：½ mv² + ½ Iω² = mgh。代入I = ⅖ mR²及v = ωR，可求得特定加速度。

Always identify the axis of rotation and keep the lever arm perpendicular to the force when calculating torque. If the force is not perpendicular, use the component that is perpendicular.

计算扭矩时，务必明确转轴，并确保力臂与力垂直。若力不垂直，则使用其垂直分量。

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7. Simple Harmonic Motion | 简谐运动

SHM FRQs focus on mass-spring systems and simple pendulums. The period of a mass-spring oscillator is T = 2π √(m/k), independent of amplitude. For a pendulum, T = 2π √(L/g) for small angles.

简谐运动FRQ集中于弹簧振子和单摆。弹簧振子的周期为T = 2π √(m/k)，与振幅无关。单摆在小角度下T = 2π √(L/g)。

Energy in SHM continuously transforms between kinetic and potential forms. At maximum displacement, energy is all potential (½ k A² for spring); at equilibrium, energy is all kinetic (½ m v_max²). Thus v_max = A √(k/m).

简谐运动中的能量在动能与势能间持续转化。在最大位移处，能量全为势能（弹簧为½ k A²）；在平衡位置，能量全为动能（½ m v_max²）。因此v_max = A √(k/m)。

An FRQ may give a position vs. time graph and ask for the spring constant or maximum acceleration. The slope of the velocity-time graph or using a_max = A (2π/T)² = A ω² can be employed.

FRQ可能给出位置-时间图像，要求求弹簧劲度系数或最大加速度。可通过速度-时间图斜率或利用a_max = A (2π/T)² = A ω²求解。

For a pendulum, the restoring force is -mg sinθ, leading to angular frequency ω = √(g/L). Changing mass does not affect the period, a common misconception addressed in FRQs.

对于单摆，回复力为-mg sinθ，角频率ω = √(g/L)。改变质量不影响周期，这是FRQ中常矫正的常见误解。

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8. Experimental Design FRQs | 实验设计题

The experimental design FRQ tests your ability to plan a lab investigation. You must state a measurable hypothesis, identify independent and dependent variables, describe the procedure with clear steps, and explain how to analyze data, often using a graph to linearize a relationship.

实验设计FRQ考察你规划实验探究的能力。你需要提出可测量假设，确定自变量与因变量，清晰描述实验步骤，并说明如何分析数据，常通过图像线性化处理关系。

A typical prompt: ‘Design an experiment to determine the coefficient of kinetic friction between a block and a surface.’ Your response should include materials, a method to measure acceleration (e.g., motion sensor or photogates), and how to use ΣF = ma to extract μₖ.

典型提示：“设计实验测定滑块与表面间的动摩擦系数。”答案应包含器材、测量加速度的方法（如运动传感器或光电门），以及如何利用ΣF = ma求得μₖ。

To reduce error, specify repeating trials, using a low-friction pulley, or taking average values. If a graph is used, explain what quantities to plot to yield a straight line whose slope or intercept gives the desired constant. For friction: plot F_net vs. F_N, slope equals μₖ.

为减小误差，需说明重复实验、使用低摩擦滑轮或取平均值。若使用图像，解释应绘制哪些量以得出一条直线，通过斜率或截距求得所需常数。对于摩擦：绘制F_net vs. F_N，斜率即为μₖ。

Common mistakes in this section include not clearly specifying how variables are controlled or not describing how raw data will be transformed. Always link your procedure directly to the physics equation you intend to verify.

此部分常见错误包括未清楚说明如何控制变量，或未描述原始数据如何转换。务必使实验步骤与你打算验证的物理方程直接挂钩。

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9. Qualitative-Quantitative Translation (QQT) | 定性定量转换题

The QQT FRQ asks you to explain why an equation predicts a certain trend. You must combine algebraic reasoning with physical concepts, often comparing two scenarios. For example: using the equation for gravitational force, F = G m₁m₂ / r², explain how doubling the orbital radius affects the force.

QQT题要求解释某一方程为何预测某种趋势。你必须结合代数推理与物理概念，常比较两种情形。例如：使用万有引力公式F = G m₁m₂ / r²，解释轨道半径加倍如何影响力的大小。

Your answer must state that because F is inversely proportional to r², doubling r reduces the force to one-fourth. Then connect this to a real-world observation: satellites in higher orbits move slower due to weaker centripetal force.

你的答案须说明由于F与r²成反比，r加倍则力减为四分之一。然后联系实际现象：轨道越高的卫星因所需向心力较小而运行较慢。

Another frequent QQT involves impulse: a car crash with an airbag increases the stopping time Δt, which decreases the average force F_avg for the same change in momentum. Express this with F_avg = Δp / Δt and explain qualitatively.

另一常见QQT涉及冲量：汽车碰撞中安全气囊延长了停车时间Δt，在动量变化相同的情况下降低了平均力F_avg。用F_avg = Δp / Δt表达并进行定性解释。

To score full points, explicitly state which variables are held constant and which one changes, then deduce the effect. Avoid vague statements; always reference the relevant equation.

要得满分，应明确指出哪些量保持不变、哪个量改变，然后推导影响。避免含糊陈述；始终引用相关方程。

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10. Common Mistakes and How to Avoid Them | 常见错误与应对

Misidentifying the system or drawing an incorrect free-body diagram is the top error. Always define your system clearly before writing equations. Include all forces acting on the chosen object, even if they later cancel.

最严重错误是错误确定系统或画错受力图。写方程前务必清晰定义系统。即使某些力最终抵消，也要先把作用在所选对象上的力全部标出。

Confusing mass and weight: mass is measured in kg and is invariant; weight is mg and depends on g. When given a scale reading in newtons, it is the normal force, not necessarily weight.

混淆质量与重量：质量以kg为单位且不变；重量为mg，取决于g。若给出秤的读数为牛顿，那是法向力，不一定是重力。

Sign errors in energy and momentum: when a spring is compressed, elastic potential energy is positive, but the work done by the spring may be negative if the displacement is opposite to the force. Use a consistent sign convention.

能量与动量中的正负号错误：弹簧被压缩时弹性势能为正，但若位移与力反向，弹簧做功可能为负。应采用一致的正负号规则。

Failing to consider the rotational energy of a rolling object: if the problem mentions ‘without slipping’, you must include ½ Iω². Many students incorrectly use only translational kinetic energy.

忽略滚动物体的转动动能：若题目提及“无滑滚动”，就必须计入½ Iω²。很多学生错误地只使用平动动能。

Not showing substitutions: on the FRQ, plugging numbers too early can lead to arithmetic errors and loss of partial credit. Solve algebraically for the target variable first, then substitute numbers with units.

不展示代入步骤：在FRQ中过早代入数字会导致计算错误，且失去部分分数。先代数求解目标变量，再代入带单位的数字。

Units and significant figures: always include units in final answers and be mindful of the precision implied by given data. Though not heavily weighted, it shows thoroughness.

单位与有效数字：最终答案务必带上单位，并注意给定数据暗示的精度。虽占分不多，但体现严谨性。

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