Year 12 CAIE Physics: Core Concepts Review | Year 12 CAIE 物理：核心知识点梳理

📚 Year 12 CAIE Physics: Core Concepts Review | Year 12 CAIE 物理：核心知识点梳理

Year 12 CAIE Physics (AS Level) builds a quantitative and experimental foundation for understanding the physical world. This article provides a concise review of the core topics, covering key equations, essential concepts, and common pitfalls that students must master to excel in the examination.

Year 12 CAIE 物理（AS阶段）为学生理解物理世界奠定了定量与实验的基础。本文对核心知识点进行简要梳理，涵盖关键方程、重要概念以及常见的易错点，帮助学生在考试中取得优异成绩。

1. Physical Quantities and Units | 物理量与单位

All physical quantities are expressed in terms of seven SI base units. Derived units are combinations of these base units, and dimensional homogeneity requires that both sides of any valid equation have the same base units. Common prefixes such as kilo (10³), mega (10⁶), milli (10⁻³), and nano (10⁻⁹) are used for convenience.

所有物理量都可以用七个国际单位制基本单位表示。导出单位则是这些基本单位的组合。量纲齐次性要求任何有效方程的两边具有相同的基本单位。常用的前缀包括千（10³）、兆（10⁶）、毫（10⁻³）和纳（10⁻⁹）。

Uncertainties are an essential part of experimental physics. Absolute uncertainty is the estimated range of a measurement, while percentage uncertainty is (absolute uncertainty / measured value) × 100%. When combining measurements, for addition/subtraction, absolute uncertainties add; for multiplication/division, percentage uncertainties add.

不确定度是实验物理的重要组成部分。绝对不确定度是测量的估计范围，百分不确定度则是（绝对不确定度/测量值）×100%。在合成测量值时，加减运算时绝对不确定度相加，乘除运算时百分不确定度相加。

2. Kinematics | 运动学

Kinematics describes motion without considering its causes. For an object moving in a straight line with constant acceleration a, initial velocity u, final velocity v, displacement s, and time t, the following equations of motion apply.

运动学描述物体的运动而不考虑引起运动的原因。对于以恒定加速度a沿直线运动的物体，设初速度为u、末速度为v、位移为s、时间为t，以下运动方程适用。

v = u + at    s = ut + ½at²    s = ½(u + v)t    v² = u² + 2as

Displacement–time and velocity–time graphs provide visual interpretations of motion. The slope of a displacement–time graph gives velocity, while the slope of a velocity–time graph gives acceleration, and the area under a velocity–time graph gives displacement.

位移-时间图和速度-时间图可以直观地解释运动。位移-时间图的斜率表示速度，速度-时间图的斜率表示加速度，而速度-时间图下的面积表示位移。

For projectile motion in a uniform gravitational field, the horizontal and vertical components of motion are independent. The horizontal velocity is constant while the vertical motion experiences constant acceleration g = 9.81 m s⁻² downward.

在均匀重力场中的抛体运动中，水平方向和竖直方向的运动相互独立。水平速度保持不变，竖直方向则受恒定加速度g = 9.81 m s⁻²作用向下。

3. Dynamics | 动力学

Newton’s three laws of motion form the backbone of dynamics. The first law states that an object remains at rest or in uniform motion unless acted upon by a net external force. The second law quantifies the effect: ∑F = ma. The third law states that for every action there is an equal and opposite reaction.

牛顿运动三定律构成了动力学的核心。第一定律指出，除非受到净外力作用，物体将保持静止或匀速直线运动状态。第二定律定量描述了力的效果：∑F = ma。第三定律表明，每有一个作用力就有一个大小相等、方向相反的反作用力。

Linear momentum is defined as p = mv. The impulse of a force equals the change in momentum: FΔt = Δp. In a closed system with no external forces, the total momentum before an interaction equals the total momentum after – this is the principle of conservation of momentum.

动量定义为p = mv。冲量等于动量的变化：FΔt = Δp。在一个无外力的封闭系统中，相互作用前的总动量等于作用后的总动量，这就是动量守恒定律。

4. Forces, Density, and Pressure | 力、密度与压强

The moment of a force about a point is the product of the force and the perpendicular distance from the point to its line of action: Moment = Fd. For an object to be in equilibrium, both the resultant force and the resultant moment must be zero.

力对某点的力矩等于力与该点到力作用线的垂直距离的乘积：力矩 = Fd。物体若要处于平衡状态，其所受的合外力和合力矩都必须为零。

Density is mass per unit volume: ρ = m/V. Pressure is force per unit area: p = F/A. The pressure due to a column of liquid of height h is p = ρgh. Archimedes’ principle states that the upthrust on an object immersed in a fluid equals the weight of the displaced fluid.

密度是单位体积的质量：ρ = m/V。压强是单位面积上的力：p = F/A。高度为h的液柱产生的压强为p = ρgh。阿基米德原理指出，浸在流体中的物体所受的浮力等于被排开流体的重量。

5. Work, Energy, and Power | 功、能量与功率

Work is done when a force moves its point of application: W = Fs cosθ, where θ is the angle between the force and the displacement direction. Energy is the capacity to do work. Kinetic energy is Eₖ = ½mv², and gravitational potential energy near Earth’s surface is ΔEₚ = mgΔh.

当力在其作用点移动时做功：W = Fs cosθ，其中θ是力与位移方向之间的夹角。能量是做功的能力。动能为Eₖ = ½mv²，地球表面附近的重力势能为ΔEₚ = mgΔh。

The principle of conservation of energy states that energy cannot be created or destroyed, only transferred or converted from one form to another. Power is the rate of doing work: P = W/t = Fv. Efficiency is the ratio of useful output energy (or power) to total input energy.

能量守恒定律指出，能量既不会凭空产生也不会凭空消失，只能从一种形式转移或转化为另一种形式。功率是做功的快慢：P = W/t = Fv。效率是有效输出能量（或功率）与总输入能量的比值。

6. Deformation of Solids | 固体的变形

Hooke’s law applies when the extension is proportional to the applied force: F = kx, where k is the spring constant. The limit of proportionality is the point beyond which Hooke’s law is no longer obeyed. Stress is force per unit cross-sectional area, and strain is extension per unit original length.

当伸长量与所施加的力成正比时，胡克定律适用：F = kx，其中k为弹簧

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