📚 Year 7 CCEA Physics: Case Study Practical Exercises | CCEA 七年级物理：案例分析实战演练
Physics helps us understand the world around us. In this article, we will work through several practical case studies that bring Year 7 CCEA physics concepts to life. Each scenario will challenge you to apply your knowledge of forces, energy, electricity, magnetism, sound, light, and more. Let’s dive in and sharpen your problem-solving skills!
物理学帮助我们理解周围的世界。在本文中，我们将通过几个实际案例分析，把 CCEA 七年级物理概念生动地呈现出来。每个情景都将考验你运用力、能量、电、磁、声、光等知识的能力。让我们开始吧，锻炼你的解决问题的能力！
1. Speeding Through the Playground | 在操场上飞跑
Tom sprints 100 metres in 15 seconds during PE class. To find his average speed, we need to use the relationship between distance, time and speed.
汤姆在体育课上用 15 秒跑了 100 米。要计算他的平均速度，我们需要用到距离、时间和速度之间的关系。
average speed = distance ÷ time
平均速度 = 距离 ÷ 时间
Plugging in Tom’s results gives: average speed = 100 m ÷ 15 s ≈ 6.67 m/s. This means he covers almost 7 metres every second. If he kept going at this speed for 60 seconds, he would cover about 400 metres.
代入汤姆的数据得到：平均速度 = 100 米 ÷ 15 秒 ≈ 6.67 米/秒。这意味着他每秒钟跑将近 7 米。如果他以这个速度跑 60 秒，大约可以跑 400 米。
Speed is a scalar quantity – it tells us how fast something moves but not the direction. If we also consider direction, we talk about velocity. For a straight run like Tom’s, his speed and the magnitude of his velocity are the same.
速度是一个标量，它告诉我们物体运动的快慢，但不表明方向。如果考虑方向，我们就需要讨论速度矢量。在汤姆这样直线奔跑的情况下，他的速率和速度大小是相同的。
2. Pushing a Heavy Box | 推沉重的箱子
Maria tries to push a large box across the classroom floor. She pushes with a force of 100 N, but the box doesn’t move. Why? Because the floor pushes back with an equal and opposite force called friction.
玛丽亚试图推动教室地板上的一个大箱子。她用了 100 牛的力，但箱子纹丝不动。为什么？因为地板给了箱子一个大小相等、方向相反的力——摩擦力。
As long as the pushing force is less than or equal to the maximum static friction, the forces are balanced and the box stays still. Once Maria pushes harder and exceeds the limit of static friction, the box will begin to slide.
只要推力小于或等于最大静摩擦力，这些力就是平衡的，箱子保持静止。一旦玛丽亚更用力推，超过了静摩擦力的极限，箱子就会开始滑动。
On a rough surface like a carpet, friction is larger, so a greater force is needed. On a smooth, icy surface, friction is much smaller. Engineers use lubricants or wheels to reduce unwanted friction in machines.
在地毯这样的粗糙表面上，摩擦力更大，因此需要更大的力。在光滑的冰面上，摩擦力则小得多。工程师使用润滑剂或轮子来减少机器中不必要的摩擦。
3. Lighting Up the Room | 点亮房间
Jack builds a simple series circuit with one cell and one bulb. The bulb glows dimly. He adds a second cell in series, and the bulb shines much brighter. Can you explain why?
杰克用一节电池和一个灯泡搭建了一个简单的串联电路。灯泡发出微弱的光。他又串联了一节电池，灯泡立刻亮了很多。你能解释这是为什么吗？
Adding cells increases the total voltage (push) in the circuit, which drives a larger current through the bulb. A higher current makes the filament hotter and radiates more light. In a parallel circuit, adding a second bulb in a separate branch does not dim the first bulb because each branch receives the full voltage.
增加电池可以提高电路的总电压（推力），从而推动更大的电流通过灯泡。更大的电流使灯丝更热，辐射出更多的光。在并联电路中，在另一条支路添加第二个灯泡并不会使第一个灯泡变暗，因为每条支路都能得到完整的电压。
If Jack adds a second bulb in series, both bulbs will be dimmer because the same current now has to pass through two bulbs, sharing the total voltage. The brightness of a bulb is a good indicator of the current flowing through it.
如果杰克串联增加第二个灯泡，两个灯泡都会变暗，因为同样的电流现在需要流过两个灯泡，总电压被分摊了。灯泡的亮度可以很好地指示流过它的电流大小。
4. Magnets in Action | 磁铁起作用了
A bar magnet has a north (N) and a south (S) pole. When Anna brings the N pole of one magnet close to the S pole of another, they snap together. When she brings two N poles together, they push apart.
一块条形磁铁有北极（N）和南极（S）。安娜把一块磁铁的 N 极靠近另一块磁铁的 S 极时，它们立刻吸在一起。当她把两个 N 极靠近时，它们互相推开。
This demonstrates the basic rule of magnetism: like poles repel, unlike poles attract. The same principle explains why a compass needle – a tiny magnet – always points north. The Earth itself acts like a giant magnet with magnetic poles near the geographic poles.
这演示了磁学的基本规律：同性相斥，异性相吸。同样的原理也解释了为什么指南针——一个小磁针——总是指向北方。地球本身就像一个巨大的磁铁，它的磁极靠近地理极点。
Magnetic forces can act at a distance without touching. The region around a magnet where it can exert a force is called its magnetic field. Iron filings sprinkled around a bar magnet reveal the pattern of the field lines.
磁力可以在不接触的情况下隔空作用。磁铁周围能够施加力的区域称为磁场。在条形磁铁周围撒上铁屑，就可以显现出磁感线的图案。
5. Echoes and Distance | 回声与距离
During a school trip to a canyon, Katie shouts and hears the echo 2 seconds later. Sound travels at about 340 m/s in air. How far away is the canyon wall?
在一次学校组织的峡谷旅行中，凯蒂大喊一声，2 秒后听到了回声。声音在空气中的传播速度约为 340 米/秒。峡谷壁有多远？
First, remember that the sound has to travel to the wall and back. So the total distance travelled by the sound in 2 seconds is: distance = speed × time = 340 m/s × 2 s = 680 m. This is the round trip. The one-way distance to the wall is therefore 680 m ÷ 2 = 340 m.
首先，记住声音需要传到岩壁再反射回来。所以声音在 2 秒内传播的总距离为：距离 = 速度 × 时间 = 340 米/秒 × 2 秒 = 680 米。这是往返距离。因此，到达岩壁的单程距离是 680 米 ÷ 2 = 340 米。
If Katie had timed the echo as 0.5 seconds, the wall would be just 85 m away. Bats and dolphins use a similar principle called echolocation to navigate and hunt in the dark.
如果凯蒂测得的回声时间是 0.5 秒，那么岩壁仅有 85 米远。蝙蝠和海豚利用相似的原理——回声定位——在黑暗中导航和捕猎。
6. Shadows Under the Sun | 阳光下的影子
On a sunny day, Liam notices that his shadow is very long in the early morning but much shorter at noon. He wonders why the length of a shadow changes during the day.
在一个晴朗的日子，利亚姆注意到清晨时他的影子很长，但到了正午就短了很多。他好奇为什么一天中影子的长度会变化。
Shadows form because light travels in straight lines. When an object blocks the light, a dark area appears behind it. The size of the shadow depends on the angle of the light source. In the morning and evening, the Sun is low in the sky, so the light hits Liam at a shallow angle, casting a long shadow. At noon, the Sun is almost overhead, so the shadow is short.
影子之所以形成，是因为光沿直线传播。当一个物体遮挡住光线时，其背后就会出现一个黑暗的区域。影子的大小取决于光源的角度。清晨和傍晚，太阳在天空中的位置较低，光线以较小的角度照射利亚姆，投下长长的影子。正午时，太阳几乎在头顶正上方，影子就变短了。
You can investigate this with a torch and an object. Move the torch closer and farther, or change its angle, and watch how the shadow size and position transform on a screen.
你可以用手电筒和物体来探究这个现象。移动手电筒靠近或远离物体，或者改变它的角度，观察屏幕上影子的大小和位置如何变化。
7. Energy from Food to Run | 从食物到奔跑的能量
Every time we run or jump, our bodies transfer stored chemical energy from food into kinetic energy and thermal energy. Energy is never created or destroyed – it is conserved, merely changing from one form to another.
每次我们奔跑或跳跃时，身体都会将食物中储存的化学能转化为动能和热能。能量既不会凭空产生也不会凭空消失——它是守恒的，只是从一种形式转化为另一种形式。
Consider a sprinter waiting at the start line. When the starting pistol fires, chemical energy in her muscles rapidly transforms into kinetic energy as she accelerates. Some energy is always ‘lost’ as heat, which is why athletes feel warm during a race. This heat energy spreads into the surroundings, becoming less useful.
想象一位短跑运动员在起跑线上等候。发令枪一响，她肌肉中的化学能迅速转化为动能，使她加速。总有一部分能量以热能的形式“流失”，这就是为什么运动员在比赛中会感到热。这些热能扩散到周围环境中，变成不太有用的能量。
Energy transfer diagrams help us track these changes. For the sprinter: chemical energy (from food) → kinetic energy (motion) + thermal energy (heat). Understanding energy transfers helps engineers design more efficient vehicles and power stations.
能量转移图能帮助我们追踪这些变化。对短跑运动员来说：化学能（来自食物）→ 动能（运动）+ 热能（热量）。理解能量转移有助于工程师设计更高效的车辆和发电站。
8. Weighing on the Moon | 在月球上称重
Sam has a mass of 40 kg on Earth. His weight is the force of gravity pulling on his mass. On Earth, the gravitational field strength is about 10 N/kg, so his weight is: weight = mass × g = 40 kg × 10 N/kg = 400 N.
萨姆在地球上的质量是 40 千克。他的重量是重力作用在他质量上的力。地球上的重力场强度大约是 10 牛/千克，所以他的重量为：重量 = 质量 × g = 40 千克 × 10 牛/千克 = 400 牛。
If Sam travels to the Moon, his mass remains 40 kg because the amount of matter in his body does not change. However, the Moon’s gravitational field strength is only about 1.6 N/kg. His weight on the Moon would be 40 kg × 1.6 N/kg = 64 N – about one sixth of his Earth weight.
如果萨姆到了月球，他的质量仍然是 40 千克，因为他身体所含物质的量没有变化。然而，月球的重力场强度只有大约 1.6 牛/千克。他在月球上的重量将变为 40 千克 × 1.6 牛/千克 = 64 牛——大约是地球重量的六分之一。
That is why astronauts can jump much higher and feel lighter on the Moon. Mass and weight are often confused in everyday language, but in physics they are distinctly different: mass is measured in kilograms, weight in newtons.
这就是为什么宇航员在月球上能跳得更高、感觉更轻。日常生活中，质量和重量经常被混淆，但在物理学中它们截然不同：质量的单位是千克，重量的单位是牛顿。
Published by TutorHao | Physics Revision Series | aleveler.com
更多咨询请联系16621398022（同微信）
屏轩国际教育cambridge primary/secondary checkpoint, cat4, ukiset,ukcat,igcse,alevel,PAT,STEP,MAT, ibdp,ap,ssat,sat,sat2课程辅导，国外大学本科硕士研究生博士课程论文辅导