IGCSE CAIE Engineering: Unit Test Mock Paper Walkthrough | IGCSE CAIE 工程：单元测试模拟卷解析

📚 IGCSE CAIE Engineering: Unit Test Mock Paper Walkthrough | IGCSE CAIE 工程：单元测试模拟卷解析

This walkthrough reviews a 40-mark unit test covering the most common IGCSE CAIE Engineering topics: materials, forces, moments, energy, electrical principles, manufacturing, CAD/CAM and safety. Each question is followed by a model answer and examiner-style comments to help you understand exactly where marks are awarded.

本解析复习一份 40 分的单元测试模拟卷，覆盖 IGCSE CAIE 工程最常见的考点：材料、力、力矩、能量、电学原理、制造工艺、CAD/CAM 与安全。每道题后给出模型答案和考官式点评，帮助你准确了解得分点。

1. How to Read the Mock Paper | 如何解读模拟卷

This mock paper contains 10 questions worth 40 marks in total. It mirrors the balance of short recall, calculation and extended response questions found in the CAIE IGCSE Engineering written papers, so time management is part of the practice.

本模拟卷共 10 题，总分 40 分。试卷结构仿照 CAIE IGCSE 工程笔试中简答、计算与扩展题的比例设计，因此时间管理也是练习的一部分。

Command words tell you what depth is required. ‘State’ means write a short fact; ‘calculate’ means show formula, substitution and unit; ‘explain’ means give a reason or cause; ‘evaluate’ means compare advantages and disadvantages before making a judgement.

指令词说明答题深度：’state’ 写出简短事实；’calculate’ 写公式、代入和单位；’explain’ 给出原因或机理；’evaluate’ 先比较优缺点再作出判断。

Always match the number of points to the marks available. For a 4-mark explanation, write four distinct engineering points: material choice, load type, safety factor and cost.

答题时，答案点数要与分值匹配。4 分解释题应写出四个不同的工程要点：材料选择、载荷类型、安全系数和成本。

2. Question 1: Material Properties | 第 1 题：材料性能

Question 1: Mild steel is often used for car chassis. State two mechanical properties that make mild steel suitable. [2]

第 1 题：低碳钢常用于汽车底盘。写出两项使低碳钢适合的力学性能。[2]

Model answer: ductility and toughness.

模型答案：延展性和韧性。

Ductility allows the chassis to be pressed into complex shapes without cracking. Toughness allows it to absorb impact energy during a collision before fracture, which improves crash safety.

延展性使底盘能冲压成复杂形状而不开裂；韧性使底盘在碰撞时先吸收冲击能量而不立即断裂，从而提高碰撞安全性。

Examiner tip: Do not confuse toughness with hardness. Toughness is energy absorbed per unit volume; hardness is resistance to indentation or scratching.

考官提示：不要把韧性与硬度混淆。韧性是单位体积吸收的能量，硬度是抵抗压痕或划痕的能力。

Mild steel contains about 0.15% to 0.30% carbon. The low carbon content improves weldability and ductility, so it is easier to join and form than high-carbon steel.

低碳钢的碳含量约为 0.15% 至 0.30%。较低的碳含量提高可焊性和延展性，因此比高碳钢更容易焊接和成形。

3. Question 2: Forces and Free-Body Diagram | 第 2 题：力与受力图

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