📚 Year 11 Cambridge Physics Formula and Theorem Quick Reference Handbook | 剑桥物理公式定理速查手册
Welcome to the essential quick reference for Year 11 Cambridge IGCSE Physics. This handbook collects the key equations, laws and relationships you must know for the examinations. Use it to revise, test yourself and build confidence in applying physics concepts. All formulas are expressed with clear symbols and consistent units. Keep this guide handy for last-minute revision.
欢迎使用这份为 Year 11 剑桥 IGCSE 物理准备的核心速查手册。本手册汇集了考试必须掌握的关键方程、定律和关系式。用它来复习、自我检测并提升应用物理概念的信心。所有公式均用清晰的符号和一致的单位表达。将这份指南放在手边，便于考前最终重温。
1. Kinematics | 运动学
When an object moves with uniform acceleration, its motion is described by the SUVAT equations. These link initial velocity u, final velocity v, acceleration a, displacement s and time t.
当物体做匀加速运动时，用 SUVAT 方程描述其运动。这些方程将初速度 u、末速度 v、加速度 a、位移 s 和时间 t 联系起来。
The first equation gives the final velocity after a period of acceleration.
第一个方程给出经过一段时间加速后的末速度。
v = u + a t
Displacement can be found when the acceleration is constant and the initial velocity is known.
当加速度恒定时，若已知初速度，便可求出位移。
s = u t + ½ a t²
The following equation bypasses time, connecting velocities, acceleration and displacement directly.
以下方程无需时间，直接联系速度、加速度与位移。
v² = u² + 2 a s
Average speed is the simplest measure, useful when acceleration is not constant.
平均速度是最简单的量度，在加速度非常数时很有用。
average speed = total distance / total time
When acceleration is uniform, displacement can also be expressed using the average of initial and final velocities.
在匀加速下，位移也可用初、末速度的平均值表示。
s = (u + v) t / 2
2. Dynamics | 动力学
Newton's second law is the foundation of dynamics: resultant force equals mass times acceleration.
牛顿第二定律是动力学的基础：合力等于质量乘以加速度。
F = m a
The weight of an object near the Earth's surface is the product of its mass and the gravitational field strength g (9.8 N/kg).
物体在地表附近的重力等于其质量与重力场强 g (9.8 N/kg) 的乘积。
W = m g
Hooke's law states that the extension x of a spring is directly proportional to the applied force F, provided the elastic limit is not exceeded.
胡克定律指出，只要不超过弹性极限，弹簧的伸长量 x 与施加力 F 成正比。
F = k x
The turning effect of a force is measured by the moment, which depends on the force and the perpendicular distance from the pivot.
力的转动效果用力矩衡量，取决于力的大小和到支点的垂直距离。
moment = F × d
For an object in rotational equilibrium, the total clockwise moment must balance the total anticlockwise moment.
物体处于转动平衡时，顺时针力矩之和必须等于逆时针力矩之和。
∑ clockwise moments = ∑ anticlockwise moments
3. Momentum | 动量
Momentum is the product of mass and velocity. It is a vector quantity, conserved in all isolated systems.
动量是质量与速度的乘积，为矢量，在所有孤立系统中守恒。
p = m v
Impulse is the change in momentum and equals the average force multiplied by the time for which it acts.
冲量是动量的变化量，等于平均作用力与作用时间的乘积。
F t = Δ p
In a collision between two objects (no external force), total momentum before equals total momentum after.
在两物体碰撞中（无外力），碰撞前总动量等于碰撞后总动量。
