📚 KS3 CIE Physics: Hooke’s Law Problems | KS3 CIE 物理：胡克定律问题
In KS3 physics, Hooke’s Law describes how springs and other elastic objects stretch when forces are applied. This article explains the law, the equation F = kx, and the types of problems you may meet in CIE-style tests, with worked examples and practice questions.
在 KS3 物理中，胡克定律描述了弹簧和其他弹性物体在受力时如何伸长。本文解释这一定律、公式 F = kx，以及 CIE 风格测试中可能遇到的各类问题，并配有例题和练习题。
1. What Is Hooke’s Law? | 什么是胡克定律？
Hooke’s Law describes the behaviour of springs and many other elastic materials. It says that the extension of a spring is directly proportional to the force applied to it, provided the elastic limit is not exceeded.
胡克定律描述弹簧和许多其他弹性材料的行为。它说的是，只要不超过弹性极限，弹簧的伸长量与施加的力成正比。
The law is named after Robert Hooke, a 17th-century English scientist. It works for metal springs, wires and some other elastic objects, but it does not apply to materials like rubber bands, which do not give a straight-line graph.
该定律以 17 世纪英国科学家罗伯特·胡克的名字命名。它适用于金属弹簧、金属丝和其他一些弹性物体，但不适用于橡皮筋等材料，因为橡皮筋无法得到直线图像。
The word ‘extension’ means the extra length produced by the force, not the total length of the spring.
‘伸长量’ 一词指的是力产生的额外长度，而不是弹簧的总长度。
2. The Hooke’s Law Equation: F = kx | 胡克定律公式 F = kx
The equation for Hooke’s Law is written as F = kx, where F is the force in newtons (N), k is the spring constant in newtons per metre (N/m), and x is the extension in metres (m).
胡克定律的公式写作 F = kx，其中 F 是力，单位牛顿 (N)；k 是弹簧常数，单位牛顿每米 (N/m)；x 是伸长量，单位米 (m)。
F = k × x
The equation can be rearranged into three useful forms: F = kx, k = F ÷ x, and x = F ÷ k. Always convert lengths to metres before substituting into the formula.
这个公式可以变形为三种有用的形式：F = kx、k = F ÷ x 和 x = F ÷ k。代入公式前，务必先将长度单位换算成米。
| Quantity | Symbol | Unit |
|---|---|---|
| Force | F | newton (N) |
| Spring constant | k | N/m |
| Extension | x | metre (m) |
在解题时，力、弹簧常数和伸长量的单位必须统一。通常长度用米，力用牛顿，弹簧常数用牛顿每米。
3. Understanding the Spring Constant k | 理解弹簧常数 k
The spring constant k tells you how stiff a spring is. A large k means the spring is stiff and needs a large force to produce a small extension. A small k means the spring is soft and stretches easily.
弹簧常数 k 表示弹簧的刚度。k 大意味着弹簧硬，需要较大的力
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