📚 In-Depth Analysis of Past Papers for Year 7 Cambridge Physics | Year 7 Cambridge 物理：历年真题深度解析
Year 7 Cambridge Physics lays the foundation for understanding how the universe behaves, from forces and energy to waves and space. Working through past papers is the most effective way to identify patterns in questions, master core concepts, and build exam confidence. This article provides a deep breakdown of frequently examined topics, with sample questions, model answers, and practical tips to help students think like an examiner.
Year 7 剑桥物理为学生理解宇宙的运行方式奠定了基础，涵盖了力、能量、波和太空等内容。钻研历年真题是识别题目规律、掌握核心概念并建立考试信心的最佳途径。本文深度剖析高频考点，提供样题、模型答案和实用技巧，帮助学生像考官一样思考。
1. Understanding Forces | 力的理解
A force is a push or a pull that can change an object’s speed, direction, or shape. In past papers, students are often asked to identify the net force from a diagram of arrows and to recall that force is measured in newtons (N). For example, if a car is pushed with 50 N to the east and friction acts with 20 N to the west, the net force is 50 N – 20 N = 30 N east.
力是推或拉，可以改变物体的速度、方向或形状。历年真题常要求学生根据箭头图识别合力，并记住力的单位是牛顿（N）。例如，若向东推汽车用了50 N，同时向西的摩擦力为20 N，则合力为50 N – 20 N = 30 N，方向向东。
Many questions also test balanced and unbalanced forces. When the net force is zero, the forces are balanced and the object remains at rest or moves at a constant speed. Unbalanced forces cause acceleration or deceleration. A typical exam problem shows a parachutist falling; initially, weight is greater than air resistance, so the speed increases, but when air resistance builds up to equal weight, terminal velocity is reached.
许多题目还会检验平衡力与非平衡力。合力为零时，力是平衡的，物体保持静止或匀速运动。非平衡力则引起加速或减速。一道典型的真题画面中，跳伞员下落：最初重力大于空气阻力，速度增加；当空气阻力增大到与重力相等时，达到终极速度。
2. Speed and Motion | 速度和运动
Speed calculations appear in nearly every Year 7 physics exam. Students must recall the formula: speed = distance ÷ time. A common question from past papers states, ‘A cyclist travels 150 metres in 30 seconds. Calculate the average speed.’ The answer is 150 m ÷ 30 s = 5 m/s.
速度计算几乎出现在每一份 Year 7 物理试卷中。学生必须记住公式：速度 = 距离 ÷ 时间。一道常见的真题：“一名自行车手在30秒内行驶了150米。计算平均速度。”答案是150 m ÷ 30 s = 5 m/s。
Examiners often ask learners to convert units, for example from minutes to seconds or from kilometres to metres. If a car travels 9 km in 0.25 hours, the speed in km/h is 9 km ÷ 0.25 h = 36 km/h. A follow-up might require converting this to m/s: 36 km/h = 36 × 1000 m / 3600 s = 10 m/s. Practice unit conversions is vital.
考官经常要求学生进行单位换算，例如将分钟换算为秒，或将公里换算为米。如果一辆车在0.25小时内行驶了9 km，速度为9 km ÷ 0.25 h = 36 km/h。后续题目可能要求转换为m/s：36 km/h = 36 × 1000 m / 3600 s = 10 m/s。熟练掌握单位换算至关重要。
Distance-time graphs are another staple. A horizontal line means the object is stationary. A straight sloping line indicates constant speed, and a steeper slope means a faster speed. Past papers may ask students to calculate the gradient of the graph to find the speed at a particular time interval.
距离-时间图也是必考题型。水平线表示物体静止。倾斜直线表示匀速运动，坡度越陡，速度越快。历年真题可能要求学生计算图像的斜率，从而求出某个时间段内的速度。
3. Energy Stores and Transfers | 能量储存与转移
The energy topic revolves around the idea that energy cannot be created or destroyed, only transferred. Past papers frequently ask students to name energy stores: kinetic, thermal, chemical, gravitational potential, elastic potential, and nuclear. For example, when a ball is thrown upwards, chemical energy in muscles is transferred to kinetic energy and then to gravitational potential energy.
能量这一主题的核心观点是：能量不能被创造或毁灭，只能被转移。历年真题常要求学生说出能量储存类型：动能、热能、化学能、重力势能、弹性能与核能。例如，当向上扔球时，肌肉中的化学能转化为动能，再转化为重力势能。
Exam questions often present a scenario, such as a wind turbine, and ask students to describe the energy transfers. A model answer: Wind has kinetic energy → blades rotate → kinetic energy in generator → electrical energy. A small amount of energy is wasted as thermal energy due to friction.
考题常给出一段情景，如风力发电机，要求学生描述能量转移。标准答案是：风具有动能 → 叶片转动 → 发电机中的动能 → 电能。由于摩擦，少量能量以热能形式耗散。
Energy efficiency calculations are also common. Efficiency = useful output energy ÷ total input energy × 100%. If a lamp uses 100 J of electrical energy and gives out 10 J of light, the efficiency is 10 ÷ 100 × 100% = 10%. The rest is emitted as heat. This highlights that energy is not lost, merely spread out.
能量效率计算同样十分常见。效率 = 有用输出能量 ÷ 总输入能量 × 100%。如果一盏灯使用了100 J电能并发出10 J光能，效率为10 ÷ 100 × 100% = 10%。其余能量以热的形式释放。这表明能量并未消失，只是分散了。
4. Electrical Circuits | 电路
Year 7 past papers expect students to draw and interpret simple circuits using standard symbols for a cell, battery, bulb, switch, buzzer, and motor. A circuit must be complete and closed for current to flow. A common mistake is drawing a short circuit without a component, which would cause the battery to overheat.
Year 7 历年真题要求学生画出并理解简单电路，使用标准符号：单个电池、电池组、灯泡、开关、蜂鸣器和电动机。电路必须完整且闭合，电流才能流通。一个常见错误是画出不包含元件的短路，这会导致电池过热。
Current is the flow of electric charge and is measured in amperes (A) using an ammeter connected in series. Voltage is the push that drives the current and is measured in volts (V) using a voltmeter connected in parallel. Past papers often ask, ‘Which component measures current and how must it be connected?’ The answer is an ammeter, connected in series.
电流是电荷的流动，单位为安培（A），使用串联的安培表测量。电压是驱动电流的推动力，单位为伏特（V），使用并联的伏特表测量。历年真题常问：“哪个元件测量电流，它应该如何连接？”答案是安培表，必须串联。
In a series circuit, there is only one loop, and the current is the same everywhere. If one bulb breaks, the whole circuit goes out. Past paper data analysis often provides a table of current readings at different points in a circuit; students must notice that the readings are identical, demonstrating the rule.
串联电路中只有一个回路，电流处处相同。如果一个灯泡烧坏，整个电路就断开。真题数据分析常提供电路不同位置的电流读数表格；学生必须观察到所有读数相同，从而证明这一规律。
5. Series and Parallel Circuits | 串联与并联电路
Parallel circuits contain two or more branches, and the total current from the battery is shared between the branches. If a bulb is removed from one branch, the other branches continue to operate. Past paper questions love to ask, ‘Why are household circuits connected in parallel?’ The answer is so that each appliance gets the full voltage and can be switched on or off independently.
并联电路包含两条或更多支路，电池输出的总电流被分配到各支路中。如果从一条支路上取下灯泡，其他支路仍能工作。历年真题很喜欢问：“为什么家庭电路采用并联？”答案是让每个电器都获得完整电压，并且能独立开关。
Examiners often give a diagram with ammeters placed in different branches and ask learners to predict unknown readings. For example, if the total current is 0.5 A and Branch 1 shows 0.2 A, Branch 2 must carry 0.3 A because 0.2 A + 0.3 A = 0.5 A. This applies Kirchhoff’s current law without naming it formally.
考官常给出带有安培表的支路图，要求学生预测未知读数。例如，若总电流为0.5 A，支路1显示0.2 A，则支路2必定是0.3 A，因为0.2 A + 0.3 A = 0.5 A。这其实是在不正式命名的前提下应用了基尔霍夫电流定律。
Voltage behaviour differs: in a series circuit, the battery voltage is shared across components, while in a parallel circuit, each loop gets the full battery voltage. A past paper might ask, ‘Why does a bulb in a parallel circuit shine brighter than an identical bulb in a series circuit?’ Because it receives a larger voltage, hence greater power.
电压的规律则不同：在串联电路中，电池电压在各个元件间分配；而在并联电路中，每个回路都获得完整的电池电压。一道真题可能会问：“为何并联电路中的灯泡比串联电路中的同款灯泡更亮？”因为它获得了更大的电压，因此功率更高。
6. Light and Shadows | 光与影子
Light travels in straight lines, which explains how shadows form. Past paper questions frequently ask students to draw ray diagrams showing how light from a source is blocked by an opaque object to create a shadow on a screen. The umbra is the fully dark region, while the penumbra is the partial shadow formed when the source is extended.
光沿直线传播，这解释了影子形成的原因。历年真题常让学生画光路图，显示光源发出的光被不透明物体阻挡，在屏上形成影子。完全黑暗的区域是本影，半影则是在扩展光源下形成的部分阴影。
Lunar and solar eclipses are exam favourites because they apply the same principle. In a solar eclipse, the Moon passes between the Sun and the Earth, casting a shadow on the Earth. Students must be able to label the umbra and penumbra on a diagram to secure full marks.
日食和月食是考试的常见内容，因为它们应用了相同原理。日食发生时，月球运行到太阳和地球之间，其影子落在地球上。学生必须能在图中标出本影和半影，才能获得满分。
Past papers also test how the size of a shadow changes with distance. Moving the object closer to the light source makes the shadow larger; moving the screen further away also increases the shadow size. This is because the light rays diverge from a point source, creating a larger area of darkness.
历年真题还考查影子大小随距离的变化。物体靠近光源会使影子变大；将屏移远同样会使影子增大。这是因为来自点光源的光线发散，形成了更大的黑暗区域。
7. Reflection of Light | 光的反射
The law of reflection states that the angle of incidence equals the angle of reflection, both measured from the normal (an imaginary line perpendicular to the mirror surface). Every paper includes a diagram where students must measure or calculate these angles. A typical question: ‘If the angle of incidence is 30°, what is the angle of reflection?’ The answer is 30°.
反射定律指出，入射角等于反射角，两者均从法线（垂直于镜面的假想线）量起。每一份试卷都会包含一个需要学生测量或计算这些角度的图示。一道典型问题：“若入射角为30°，反射角是多少？”答案为30°。
A common exam task is to complete a ray diagram by drawing the reflected ray using a ruler and protractor. Students must ensure the ray is straight, the angles are equal, and arrows indicate direction. Neatness matters; freehand sketches lose marks.
一项常见的考试任务是利用直尺和量角器画出反射光线，从而完成光路图。学生必须确保光线笔直、角度相等，并用箭头标示方向。卷面整洁十分重要；随手勾画会被扣分。
Smooth surfaces produce clear reflections (specular reflection), whereas rough surfaces scatter light in all directions (diffuse reflection). Past papers often ask why you can see a reflection in a mirror but not on a sheet of paper. The explanation: the mirror is smooth, so light rays reflect at the same angle; paper is rough, so light is scattered.
光滑表面产生清晰的反射（镜面反射），而粗糙表面则向各个方向散射光线（漫反射）。历年真题常问为何能在镜子里看到反射像，而在一张纸上却看不到。解释是：镜子表面光滑，所有光线以相同角度反射；纸张粗糙，光线被散射。
8. Sound and Vibrations | 声音与振动
Sound is caused by vibrations that travel through a medium such as air, water, or wood. A crucial concept tested in past papers is that sound cannot travel through a vacuum because there are no particles to vibrate. A bell jar experiment, where the ringing sound fades as air is pumped out, illustrates this perfectly.
声音是由振动引起的，振动通过空气、水或木头等介质传播。历年真题测试的一个重要概念是，声音不能在真空中传播，因为没有粒子可以振动。钟罩实验完美地说明了这一点：随着空气被抽出，铃声逐渐减弱。
The frequency of a sound wave determines its pitch; amplitude determines loudness. If an oscilloscope trace shows more waves in the same time period, the pitch is higher. A taller wave indicates a louder sound. Past paper questions often present two oscilloscope images and ask which sound is higher in pitch or louder.
声波的频率决定音高，振幅决定响度。如果示波器显示的波形在相同时间内周期更密集，音高就更高；波幅更高则表示声音更响。历年真题常给出两幅示波器图像，问哪个声音音高更高或更响。
The human ear detects sound through a sequence: ear canal → eardrum → tiny bones → cochlea → auditory nerve. Although the required detail is basic, students must know that the eardrum vibrates when sound waves hit it, and these vibrations are converted into electrical signals for the brain.
人耳通过以下顺序探测声音：耳道 → 鼓膜 → 听小骨 → 耳蜗 → 听觉神经。虽然要求的细节不多，但学生必须知道声波撞击鼓膜时会引起振动，而这些振动会被转换为电信号传送至大脑。
9. The Solar System | 太阳系
Year 7 astronomy questions focus on the order of planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune. A common exam task is to label a diagram or complete a table of planet properties. Jupiter is the largest, Saturn has prominent rings, and Earth is the only planet known to support life.
Year 7 的天文学题目侧重于行星顺序：水星、金星、地球、火星、木星、土星、天王星、海王星。常见的考试任务是给图表标注或完成行星属性表格。木星体积最大，土星有明显的环，而地球是已知唯一存在生命的行星。
Seasons are caused by the tilt of the Earth’s axis, not by changing distance from the Sun. Past papers often ask, ‘Explain why it is summer in the northern hemisphere when it is winter in the southern hemisphere.’ The answer: the northern hemisphere is tilted towards the Sun, receiving more direct sunlight and longer days.
季节是由地轴倾斜造成的，而不是与太阳距离的变化。历年真题经常问：“请解释为何北半球是夏天时南半球却是冬天。”答案是：北半球向太阳倾斜，获得更直接的光照和更长的白昼时间。
The Moon orbits the Earth, causing lunar phases. A new moon occurs when the Moon lies between the Earth and the Sun; a full moon occurs when the Earth is between the Moon and the Sun. Past paper diagrams frequently require students to draw the relative positions of the Sun, Earth, and Moon for specific phases.
月球围绕地球运行，形成月相。当月球位于地球和太阳之间时为新月；当地球位于月球和太阳之间时为满月。历年真题图示常要求学生画出太阳、地球和月球在不同月相时的相对位置。
10. Exam Technique and Common Pitfalls | 考试技巧与常见错误
Past papers reveal that many marks are lost not because of lack of knowledge, but because of misreading the question. Always highlight keywords like ‘calculate’, ‘describe’, ‘explain’, or ‘compare’. A ‘describe’ question only needs what you see; an ‘explain’ question must give a reason using scientific principles.
历年真题显示，许多分数的丢失并非知识欠缺，而是审题不仔细。务必圈出关键词，如“计算”、“描述”、“解释”或“比较”。“描述”题只需说出所见现象；“解释”题必须用科学原理给出理由。
Units are non-negotiable. Leaving them out in a calculation answer can cost a mark. Always include the correct unit: m for distance, s for time, m/s for speed, N for force, J for energy, V for voltage, A for current. Double-check conversions: 1 km = 1000 m, 1 hour = 3600 s.
单位绝不能省略。计算题答案中漏写单位会被扣分。一定要写下正确的单位：距离用米（m），时间用秒（s），速度用米每秒（m/s），力用牛顿（N），能量用焦耳（J），电压用伏特（V），电流用安培（A）。再三检查单位换算：1 km = 1000 m，1小时 = 3600 s。
A final piece of advice is to use diagrams effectively. Drawing force arrows in the correct direction, labelling keys on a graph, and sketching a ray diagram with a ruler can all earn marks. Leave no blank answer; even a partially correct formula or definition can score partial credit in Cambridge science exams.
最后一点建议是有效使用图表。正确画出力的箭头方向、标注图表关键信息、利用尺子绘制光路图，这些都可以得分。绝不空题；即便只写出部分公式或定义，在剑桥科学考试中也能获得部分分数。
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