Forces: Vectors and Moments | 力：向量与力矩

📚 Forces: Vectors and Moments | 力：向量与力矩

In the CIE A-Level Physics syllabus, the topic “Forces: vectors and moments” brings together the vector nature of force, the conditions for translational and rotational equilibrium, and practical applications such as levers, beams and tipping. A strong grasp of these ideas is essential for solving statics problems.

在 CIE A-Level 物理大纲中，“力：向量与力矩”这一主题综合了力的向量性质、平动与转动平衡条件，以及杠杆、横梁和翻倒等实际应用。扎实掌握这些概念对解决静力学问题至关重要。

1. Scalar and vector quantities | 标量与向量

Physical quantities in mechanics are divided into scalars and vectors. A scalar has magnitude only; examples include distance, speed, mass, energy, time and temperature. A vector has both magnitude and direction; examples include displacement, velocity, acceleration, force and momentum. Addition of scalars follows ordinary arithmetic, whereas addition of vectors must account for direction.

力学中的物理量分为标量和向量。标量只有大小，例如距离、速率、质量、能量、时间和温度。向量既有大小又有方向，例如位移、速度、加速度、力和动量。标量相加遵循普通算术法则，而向量相加必须考虑方向。