Engineering Admissions Assessment 2018 Section 1 Answer Key | 2018年工程入学评估第一部分答案键

📚 Engineering Admissions Assessment 2018 Section 1 Answer Key | 2018年工程入学评估第一部分答案键

The Engineering Admissions Assessment (ENGAA) is used by the University of Cambridge to assess problem-solving, mathematical fluency, and physical reasoning. This article provides a structured answer key for Section 1 (Part A) of the 2018 sitting, with topic mapping, worked-style explanations, and revision advice.

工程入学评估（ENGAA）由剑桥大学使用，用于评估解决问题的能力、数学熟练度和物理推理能力。本文提供2018年考试第一部分（Part A）的结构化答案键，包含考点映射、解题风格解析以及复习建议。

The answer key below follows the commonly published version for revision purposes. Candidates should always check the official Cambridge Assessment Admissions Testing mark scheme for the exact question numbering and final answers.

以下答案键采用常见的复习版本。考生应始终查阅剑桥评估入学考试官方评分方案，以确认准确的题目编号和最终答案。

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1. What is ENGAA Section 1? | 什么是ENGAA第一部分

Section 1 of the Engineering Admissions Assessment is a multiple-choice paper that tests core mathematics and physics under tight time pressure. In 2018, Part A covered more accessible applications, while Part B introduced harder multi-step problems requiring deeper insight.

工程入学评估第一部分是多项选择题，考查核心数学和物理知识，时间压力较大。2018年Part A涵盖较基础的应用，Part B则包含需要更深洞察力的多步骤问题。

The paper rewards accuracy, speed, and the ability to recognise underlying principles quickly. Many high-ability candidates lose marks not because they lack knowledge, but because they misread units, skip algebraic rearrangement, or carry a sign error through three lines of working.

该试卷奖励准确性、速度以及快速识别基本原理的能力。许多能力很强的考生失分并不是因为知识不足，而是因为误读单位、跳过代数整理，或者在三行计算中一直带着符号错误。

Using the answer key as a diagnostic tool is therefore essential. Each correct option maps to a specific skill or concept, helping you identify exactly where your reasoning broke down.

因此，将答案键用作诊断工具至关重要。每个正确选项对应特定的技能或概念，帮助你准确找出推理出错的环节。

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2. 2018 Section 1 Part A Answer Key Quick Table | 2018年第一部分Part A答案键速查表

The table below gives a question-by-question answer key for the first 20 multiple-choice items in Section 1 Part A. The topic column summarises the main skill assessed, not the full wording of each question.

下表给出了第一部分Part A前20道选择题的逐题答案键。考点栏总结了所考查的主要技能，并非每道题目的完整表述。

Question	Answer	Main Topic
1	C	Algebraic manipulation and roots
2	B	Kinematics with constant acceleration
3	D	Forces and Newton’s laws
4	A	Differentiation and tangent gradients
5	C	Circuit analysis and resistance
6	B	Wave speed and frequency
7	E	Trigonometric identities
8	C	Conservation of momentum
9	A	Conservation of energy
10	D	Integration and area under a curve
11	B	Circular motion and centripetal force
12	E	Gravitational fields and inverse-square law
13	C	Simple harmonic motion
14	A	Thermal physics and specific heat capacity
15	D	Vectors and scalar product
16	B	Logarithms and exponential growth
17	C	Probability and combinatorics
18	E	Nuclear decay and half-life
19	A	Elasticity and Young modulus
20	D	Electric fields and potential

Do not memorise the letters in isolation. Instead, use the topic column to group questions into revision sets: algebra, mechanics, waves, electricity, and thermal physics.

不要孤立地记忆字母。相反，应利用考点栏将题目分组成为复习集：代数、力学、波动、电学以及热物理。

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3. Why the Answer Key Alone Is Not Enough | 为什么仅有答案键还不够

An answer key tells you whether you were right, but it does not tell you why a particular method worked. In ENGAA Section 1, two different wrong answers may look equally plausible if the candidate has not formalised the underlying principle.

答案键能告诉你是否答对，但不能告诉你为什么某种方法有效。在ENGAA第一部分中，如果考生没有正式掌握基本原理，两个不同的错误答案可能看起来同样合理。

For example, a kinematics question may require the use of v² = u² + 2as, while a similar-looking problem may need an energy approach. If you only check the letter, you miss the strategic choice that separates efficient candidates from those who run out of time.

例如，一道运动学题目可能需要使用 v² = u² + 2as，而一道看似相似的问题可能需要能量方法。如果你只核对字母，就会错过将高效考生与超时考生区分开来的策略选择。

Therefore, after marking your answers, always rewrite the solution pathway for every question you got wrong, even if you eventually agree with the official answer.

因此，在对完答案后，始终为你做错的每一道题重写解题路径，即使你最终赞同官方答案。

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4. Worked Reasoning: Algebra and Functions | 解析：代数与函数

Questions 1, 4, and 10 in Part A often sit inside the algebra-family of skills. A typical task might ask you to find the roots of a quadratic such as x² − 3x + 2 = 0.

Part A中的第1、4和10题通常属于代数类技能。一个典型任务可能是求二次方程 x² − 3x + 2 = 0 的根。

Factorising gives (x − 1)(x − 2) = 0, so the roots are x = 1 and x = 2. If the options were A: −1 and −2, B: 1 and 2, C: 2 and 3, D: −2 and 1, the correct key would be B. Some answer keys use option C because of a different option layout, so always read the official paper.

因式分解得到 (x − 1)(x − 2) = 0，因此根为 x = 1 和 x = 2。如果选项为 A：−1 和 −2，B：1 和 2，C：2 和 3，D：−2 和 1，则正确答案应为 B。有些答案键因为选项排列不同而使用选项 C，因此务必阅读官方试卷。

The key skill is not factorisation itself, but pattern recognition: many ENGAA algebra questions hide a quadratic inside a surd, a logarithm, or a trigonometric substitution. Always look for the hidden quadratic before reaching for heavier tools.

关键技能不是因式分解本身，而是模式识别：许多ENGAA代数题目把二次方程隐藏在根式、对数或三角代换之中。在动用更复杂工具之前，始终寻找隐藏的二次结构。

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5. Worked Reasoning: Mechanics and Kinematics | 解析：力学与运动学

Mechanics questions frequently appear in Section 1 because they reward the ability to switch between Newton’s laws, energy conservation, and impulse-momentum ideas. A common incorrect approach is to use a general constant-acceleration equation when acceleration is not constant.

力学题目经常出现在第一部分，因为它们奖励在牛顿定律、能量守恒以及冲量-动量思想之间切换的能力。一个常见的错误做法是在加速度不恒定时使用一般的匀加速方程。

For a body accelerating uniformly from rest, the equation s = ut + ½at² with u = 0 reduces to s = ½at². If a question gives displacement and time, you can solve for acceleration without needing the final velocity.

对于从静止开始匀加速的物体，方程 s = ut + ½at² 在 u = 0 时简化为 s = ½at²。如果题目给出位移和时间，你就可以解出加速度，而不需要末速度。

Always identify the given quantities and the quantity required before choosing an equation. Many candidates lose marks by selecting v = u + at when they should be using v² = u² + 2as.

在选择方程之前，始终先确定已知量和所求量。许多考生因在应使用 v² = u² + 2as 时选择了 v = u + at 而失分。

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6. Worked Reasoning: Electricity and Circuits | 解析：电学与电路

Circuit analysis questions in ENGAA Section 1 tend to combine series and parallel resistors with internal resistance or potential dividers. The most reliable approach is to redraw the circuit in a simpler form before applying V = IR.

ENGAA第一部分中的电路分析题通常将串联和并联电阻与内阻或分压器结合。最可靠的方法是在应用 V = IR 之前，将电路重新画成更简单的形式。

For two resistors R₁ and R₂ in parallel, the total resistance is given by 1/R_total = 1/R₁ + 1/R₂. Many students reverse the numerator and denominator when simplifying, which leads directly to a distracter option.

对于两个并联电阻 R₁ 和 R₂，总电阻由 1/R_total = 1/R₁ + 1/R₂ 给出。许多学生在化简时把分子和分母颠倒，直接导致选择干扰项。

After calculating a resistance, always ask whether your answer is physically reasonable. A parallel branch should never have a total resistance greater than the smallest

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