OCR Science: Formula Reference Handbook | OCR 科学：公式汇总手册

📚 OCR Science: Formula Reference Handbook | OCR 科学：公式汇总手册

This handbook gathers the essential equations you need for OCR Science courses, including Physics, Chemistry and Biology. Each formula is presented clearly, with variable definitions and the context in which it is applied. Use this reference to strengthen your recall, practise numerical questions and feel confident when tackling the equation-based parts of your exams.

本手册汇集了 OCR 科学课程（涵盖物理、化学和生物）所需的核心公式。每个公式都清晰呈现，配有变量说明和适用情境。你可以借助这份参考资料巩固记忆、练习计算题，并在考试中自信地解决涉及公式的题目。

1. Motion and SUVAT Equations | 运动学与匀加速方程

average speed = distance ÷ time     v = s ÷ t

The relationship between distance travelled (s), time taken (t) and average speed (v) is fundamental in kinematics. When an object moves at a constant speed or when you need the mean speed over a journey, you simply divide the total distance by the total time. Distance is measured in metres (m) and time in seconds (s), giving speed in metres per second (m/s).

行驶距离(s)、所用时间(t)和平均速度(v)之间的关系是运动学的基础。当物体匀速运动或你需要计算全程平均快慢时，只需用总距离除以总时间。距离以米(m)为单位，时间以秒(s)为单位，速度的单位是米每秒(m/s)。

acceleration     a = (v − u) ÷ t

Acceleration (a) describes the rate at which an object’s velocity changes. It is found by subtracting the initial velocity (u) from the final velocity (v) and dividing by the time (t) over which the change occurs. Acceleration can be positive (speeding up) or negative (slowing down). The standard unit is m/s².

加速度(a)描述物体速度变化的快慢。它等于末速度(v)减初速度(u)再除以变化所用的时间(t)。加速度可以为正（加速）或负（减速）。标准单位是 m/s²。

v = u + a t

This is the first SUVAT equation for uniformly accelerated motion. It allows you to calculate the final velocity when the initial velocity, constant acceleration and time are known. It assumes acceleration does not change during the period considered.

这是匀加速运动的第一个 SUVAT 方程。当已知初速度、恒定的加速度和时间时，可以用它求出末速度。前提是所考虑的时间内加速度保持不变。

v² = u² + 2 a s

Use this equation when you do not know the time taken. It links the square of the final velocity to the square of the initial velocity, twice the acceleration and the displacement (s). The displacement is the distance moved in a straight line from the starting point.

当不知道所用时间时使用这个方程。它将末速度的平方与初速度的平方、两倍加速度以及位移(s)联系起来。位移是从起点沿直线移动的距离。

s = ((u + v) ÷ 2) × t

For uniform acceleration the average velocity is simply (u+v)/2. Multiplying the average velocity by the time gives the displacement. This equation is particularly useful when acceleration itself is not given but the initial and final speeds are known.

在匀加速情况下，平均速度就是(u+v)/2。用平均速度乘以时间便可得到位移。当没有直接给出加速度但已知初速度和末速度时，这个公式非常实用。

2. Forces and Newton’s Second Law | 力与牛顿第二定律

resultant force = mass × acceleration     F = m a

Newton’s second law states that the acceleration of an object is directly proportional to the resultant force acting on it and inversely proportional to its mass. The resultant force (F) is measured in newtons (N), mass (m) in kilograms (kg), and acceleration (a) in m/s². This equation can be used to analyse the motion of vehicles, falling objects and any system where forces are unbalanced.

牛顿第二定律指出，物体的加速度与作用在其上的合力成正比，与物体的质量成反比。合力(F)的单位是牛顿(N)，质量(m)为千克(kg)，加速度(a)为 m/s²。该公式可用于分析车辆、落体以及任何受力不平衡系统的运动。

weight = mass × gravitational field strength     W = m g

Weight (W) is the force of gravity acting on an object. On Earth the gravitational field strength (g) is approximately 9.8 N/kg. Because weight is a force, it is measured in newtons. Do not confuse weight with mass; mass remains the same everywhere, whilst weight depends on the local gravitational field.

重量(W)是作用在物体上的重力。在地球表面，重力场强度(g)约为 9.8 N/kg。由于重量是力，它的单位是牛顿。切勿将重量与质量混淆；质量在任何地方都相同，而重量取决于当地的重力场。

force = spring constant × extension     F = k x

For a spring that

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