📚 Year 8 WJEC Engineering: Interdisciplinary Integrated Problem-Solving Practice | WJEC 八年级工程：跨学科综合题型训练
Engineering at this level blends mathematics, science and design to solve real-world problems. This article presents a series of integrated question types to build confidence in tackling cross-disciplinary challenges typical of the WJEC Year 8 curriculum.
工程学科在这个阶段融合了数学、科学和设计，以解决现实问题。本文提供一系列跨学科综合题型训练，帮助你从容应对 WJEC 八年级课程中常见的综合挑战。
1. Understanding the Design Brief | 理解设计概要
A design brief communicates the problem, user needs, constraints and the measure of success. You must extract the key technical requirements before any practical work begins.
设计概要传达了问题、用户需求、限制条件和成功标准。你必须在任何实际工作开始前提取出关键技术要求。
Example brief: “Design a hand-powered lifting device to raise a 500 g load vertically by at least 300 mm. It must be stable, use no more than three simple machines, and be built from recycled classroom materials.”
示例概要：“设计一个手动提升装置，将 500 g 负载垂直提升至少 300 mm。该装置必须稳定、使用不超过三种简单机械，并由可回收的课堂材料搭建。”
- Identify the load: 500 g mass → weight ≈ 5 N (using g = 10 N/kg).
识别载荷：500 g 质量 → 重量约 5 N（取 g = 10 N/kg）。 - Key dimension: vertical lift ≥ 300 mm.
关键尺寸：垂直提升高度 ≥ 300 mm。 - Constraints: manual power, max three simple machines, recycled materials only.
限制条件：手动驱动、最多三种简单机械、仅限回收材料。
2. Mathematical Calculations: Gear Ratios and Forces | 数学计算：齿轮比与力
Integrated problems often require you to calculate speed, torque or mechanical advantage. Master gear ratios and lever principles.
综合题型常要求你计算速度、扭矩或机械效益。掌握齿轮比和杠杆原理。
Problem: A driving gear has 20 teeth and a driven gear has 60 teeth. The input shaft turns at 150 rpm. Calculate the output speed and the torque ratio.
题目：主动齿轮有 20 齿，从动齿轮有 60 齿。输入轴转速为 150 rpm。计算输出转速和扭矩比。
Gear ratio (velocity ratio) = Ndriven / Ndriver = 60 / 20 = 3 : 1.
齿轮比（速度比）= 从动齿数 / 主动齿数 = 60 / 20 = 3 : 1。
Output speed = Input speed / gear ratio = 150 / 3 = 50 rpm.
输出转速 = 输入转速 / 齿轮比 = 150 / 3 = 50 rpm。
rque ratio = inverse of speed ratio. Output torque ≈ Input torque × 3 (ignoring friction).
扭矩比 = 速度比的倒数。输出扭矩 ≈ 输入扭矩 × 3（忽略摩擦）。
Mechanical advantage = Load / Effort = Ndriven / Ndriver
机械效益 = 负载 / 动力 = Ndriven / Ndriver
3. Material Properties and Selection | 材料性能与选择
Choosing the right material depends on strength, stiffness, density, cost and workability. WJEC exams expect you to justify your choice with data from a provided table.
选择合适的材料取决于强度、刚度、密度、成本和可加工性。WJEC 考试要求你根据提供的表格数据论证你的选择。
| Material | Tensile strength (MPa) | Density (g/cm³) | Cost | Recyclability |
| Pine wood | 40 | 0.5 | Low | Yes |
| Aluminium alloy | 300 | 2.7 | Medium | Yes |
| Mild steel | 500 | 7.8 | Medium | Yes |
| Acrylic | 70 | 1.2 | Low | Limited |
Question: Which material would you choose for the load-bearing arm of the lifting device? Justify your answer using two properties from the table.
问题：你会选择哪种材料制作提升装置的承重臂？请使用表格中的两项性能加以论证。
Model answer: Aluminium alloy – it has high tensile strength (300 MPa) to safely support the 5 N load without bending, and its density is only 2.7 g/cm³, keeping the arm lightweight so less effort is needed to lift it.
参考答案：铝合金——它具有高抗拉强度（300 MPa），能安全支撑 5 N 负载而不弯曲；其密度仅为 2.7 g/cm³，可使手臂轻便，从而减少提升所需的力量。
4. Electronics and Control Systems | 电子与控制系统
A motorised version of your device might use a simple DC motor. Controlling motor direction requires a double-pole double-throw (DPDT) switch. You may be asked to complete a circuit diagram.
如果你将装置改为电动版本，可能会使用一个简单的直流电机。控制电机转向需要一个双刀双掷（DPDT）开关。考试可能要求你补全电路图。
Task: Draw or describe how to connect a DPDT switch, a 6 V battery and a DC motor so that flipping the switch reverses the motor's rotation.
任务：画出或描述如何连接一个 DPDT 开关、一个 6 V 电池和一个直流电机，使拨动开关即可反转电机旋转方向。
When the switch is in Position A, current flows through the motor from positive to negative, making it turn clockwise. In Position B, the current direction is reversed, turning the motor anticlockwise.
当开关处于位置 A 时，电流从正极流向负极通过电机，使其顺时针旋转。在位置 B 时，电流方向反转，电机逆时针旋转。
V = I × R, Ohm’s law may appear if resistors are added.
V = I × R，如果加入电阻，可能会用到欧姆定律。
5. Sketching and Technical Drawing | 草图绘制与技术制图
You are expected to produce clear 2D sketches with labels, dimensions and relevant views (front, side, plan). Use correct line types: thick continuous lines for visible edges, dashed lines for hidden details.
你需要绘制清晰的二维草图，包含标注、尺寸和相应视图（正视图、侧视图、俯视图）。使用正确的线型：粗实线表示可见边缘，虚线表示隐藏细节。
Practice: Sketch the front view of your lifting device. Include the base, support column, lever arm and the bucket holding the 500 g mass. Label the pivot and effort points.
练习：画出提升装置的正视图。包括底座、支撑柱、杠杆臂以及盛放 500 g 质量的容器。标注支点和施力点。
nd and the load lifted at the other. Use a ruler and add dimensions such as the height (≥300 mm lift).
好的草图会展示一个三角形底座以保证稳定性、一根竖直立柱、一根在中间附近转动的杠杆，一端向下施加力，另一端提升负载。使用尺子并添加尺寸，例如高度（提升行程 ≥300 mm）。
6. Structural Analysis: Trusses and Loads | 结构分析：桁架与载荷
When a structure uses trusses, you can identify tension and compression. A typical question asks you to label members in a simple triangular truss.
当结构使用桁架时，你可以识别拉力和压力。典型的题目会要求你标注出简单三角形桁架中的杆件受力情况。
Given: A simple triangular frame supports a weight hanging from the apex. The two sloping members meet at the top and join at the base nodes which are fixed.
已知：一个简单三角形框架在顶点悬挂重物。两个斜杆在顶部相交，底部节点固定。
The top sloping members are in compression, pushing towards the nodes. The base horizontal member is in tension, preventing the legs from spreading apart.
顶部斜杆受压，向节点推挤。底部水平杆受拉，防止两腿张开。
Force triangle: F1 + F2 + W = 0 (vector sum).
力三角形：F₁ + F₂ + W = 0（矢量和）。
7. Sustainability and Lifecycle | 可持续性与生命周期
Engineers must consider the environmental impact of a product from raw material extraction to disposal. This is called a Lifecycle Assessment (LCA).
工程师必须考虑产品从原材料提取到废弃处理的环境影响，这称为生命周期评估（LCA）。
Question: Compare the sustainability of using pine wood versus aluminium for the base of the device. Mention two stages of the lifecycle.
问题：比较使用松木与铝合金制作装置底座的可持续性。提及生命周期的两个阶段。
Pine wood is a renewable material with low embodied energy; at end-of-life it can be composted or burned for energy. However, if not sourced sustainably it contributes to deforestation. Aluminium requires high energy to extract but is highly recyclable without loss of properties, significantly reducing future energy use.
松木是可再生材料，蕴含能量低；在其生命周期结束时，可堆肥或焚烧供能。但如果来源不可持续，则会导致森林砍伐。铝的提取需要大量能源，但铝可高度回收且不损失性能，从而显著降低未来的能源消耗。
In the WJEC context, always connect your answer to the '6 Rs': Reduce, Reuse, Recycle, Repair, Refuse, Rethink.
在 WJEC 的语境中，始终要将你的回答与"6R"原则联系起来：减少使用、重复使用、循环回收、维修、拒绝、重新思考。
8. Testing and Evaluation Methods | 测试与评估方法
After building a prototype, you must test it against the design specification and suggest improvements. Typical tests for a lifting device focus on functionality, stability and safety.
建造原型后，你必须对照设计规格进行测试，并提出改进建议。对提升装置的典型测试侧重于功能性、稳定性和安全性。
| Test | How to carry it out | Expected result |
| Lift capacity | Attach the 500 g load and operate the mechanism 10 times. | The load is raised smoothly each time to ≥ 300 mm. |
| Stability | Apply a sideways force of 2 N to the top of the column while loaded. | The device does not tip over; the base stays flat. |
| Ease of use | Ask three classmates to operate it and time the lift. | Average lift time < 5 seconds; no confusion with controls. |
Evaluation should reference quantitative data where possible. For example, “The lift height averaged 310 mm, exceeding the 300 mm target.”
评估应尽可能引用定量数据。例如，“平均提升高度为 310 mm，超过了 300 mm 的目标。”
9. Integrated Problem: Building a Lifting Crane | 综合问题：搭建起重机
Now combine all the disciplines into one complete scenario. Use the following specifications:
现在将所有学科整合到一个完整情境中。使用以下规格：
- Power source: hand crank with a gear train (driver 15 teeth, driven 45 teeth).
动力源：带有齿轮系的手柄（主动轮 15 齿，从动轮 45 齿）。 - Structure: wooden frame with triangular bracing, base 200 mm × 200 mm.
结构：带三角支撑的木框架，底座 200 mm × 200 mm。 - Electronics: optional motor with DPDT switch and 9 V battery.
电子部分：可选电机，配 DPDT 开关和 9 V 电池。 - Target: lift 400 g to a height of 250 mm in under 3 seconds when motorised.
目标：电动时在 3 秒内将 400 g 提升至 250 mm 高度。
d = circumference × rev/s. Circumference = 2πr = 62.8 mm; 40 rpm = 0.67 rev/s → linear speed ≈ 42 mm/s. To lift 250 mm, time = 250/42 ≈ 6 s, which fails the 3-second target. Solution: reduce the gear ratio or increase drum radius. This is a classic trade-off between speed and torque.
如果电机转速为 120 rpm，计算输出转速。齿轮比 = 45/15 = 3:1，因此输出转速 = 120/3 = 40 rpm。若卷筒半径为 10 mm，线速度 = 周长 × 转/秒。周长 = 2πr = 62.8 mm；40 rpm = 0.67 转/秒 → 线速度 ≈ 42 mm/s。提升 250 mm 需要时间 = 250/42 ≈ 6 秒，未达到 3 秒目标。解决办法：减小齿轮比或增大卷筒半径。这是速度与扭矩之间的经典权衡。
10. Common Mistakes and How to Avoid Them | 常见错误与避免方法
Drawing a line under your calculation without units, mixing up driver and driven gears, and ignoring friction are all frequent pitfalls. Always double-check your ratio direction.
在计算下方画线而不写单位、混淆主动轮与从动轮、忽略摩擦，都是常见陷阱。务必仔细检查比率的方向。
Another typical error is stating a material is strong without linking to the specific data from the table. Use numbers: “Tensile strength of 500 MPa” is better than “It is very strong”.
另一个典型错误是声称某种材料坚固，却未与表格中的具体数据联系起来。要使用数字：“抗拉强度 500 MPa”比“它非常坚固”更好。
In your sketch, missing the pivot symbol (a small triangle) or not showing the range of motion can lose marks. Always include the direction of effort and load with arrows.
在草图中，缺少支点符号（小三角形）或没画出运动范围都会丢分。请务必用箭头标出施力方向和负载方向。
Published by TutorHao | Engineering Revision Series | aleveler.com
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