Year 7 CCEA Physics: Case Study Practical Exercises | Year 7 CCEA 物理：案例分析实战演练

📚 Year 7 CCEA Physics: Case Study Practical Exercises | Year 7 CCEA 物理：案例分析实战演练

In Year 7 CCEA Physics, applying your knowledge to real-world case studies helps you understand concepts deeply and prepares you for assessments. This article presents eight practical case studies covering speed, forces, circuits, echoes, mirrors, density, springs and energy conversions. Each case study includes a scenario, step-by-step analysis and worked solutions – all in clear, paired English and Chinese explanations.

在 Year 7 CCEA 物理中，将所学知识应用于实际案例分析有助于深入理解概念并为考试做好准备。本文精选了八个实战案例，涵盖速度、力、电路、回声、镜子、密度、弹簧和能量转换。每个案例都配有情境描述、逐步分析和解答——全部采用中英配对讲解，方便学习。

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1. Case Study: Calculating Average Speed | 案例分析：计算平均速度

A student runs a 100 m race in 14 seconds. Calculate her average speed in metres per second (m/s). Then convert this speed to kilometres per hour (km/h).

一名学生用14秒跑完100米。计算她的平均速度（单位：米/秒）。然后将这个速度换算为千米/小时。

Step 1: Write down the known values: distance d = 100 m, time t = 14 s.

步骤1：写下已知值：距离 d = 100 m，时间 t = 14 s。

Step 2: Use the speed formula. Average speed is total distance divided by total time.

步骤2：使用速度公式。平均速度等于总距离除以总时间。

v = d / t

Step 3: Substitute the values: v = 100 m ÷ 14 s ≈ 7.14 m/s.

步骤3：代入数值：v = 100 m ÷ 14 s ≈ 7.14 m/s。

Step 4: To convert m/s to km/h, multiply by 3.6 (since 1 m/s = 3.6 km/h). 7.14 m/s × 3.6 ≈ 25.7 km/h.

步骤4：将米/秒转换为千米/小时，乘以3.6（因为1 m/s = 3.6 km/h）。7.14 m/s × 3.6 ≈ 25.7 km/h。

The runner’s average speed is about 7.14 m/s, which is roughly 25.7 km/h. This is faster than a typical cyclist.

这名跑步者的平均速度约为7.14 m/s，约合25.7 km/h，比一般骑自行车的人还快。

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2. Case Study: Pushing a Box and Friction | 案例分析：推箱子与摩擦力

A person pushes a heavy box on a floor with a force of 200 N to the right. Friction between the box and the floor acts with 150 N to the left. The box has a mass of 50 kg. Determine the resultant force and describe the motion of the box.

一个人用200 N的力向右推一个沉重的箱子。箱子与地面之间的摩擦力为150 N，方向向左。箱子的质量为50 kg。确定合力并描述箱子的运动。

Identify the forces: applied force = 200 N right, friction = 150 N left.

识别力：推力 = 200 N 向右，摩擦力 = 150 N 向左。

Resultant force = 200 N – 150 N = 50 N to the right. Forces are unbalanced.

合力 = 200 N – 150 N = 50 N，方向向右。力的作用不平衡。

According to Newton’s Second Law, an unbalanced force causes acceleration. The box accelerates to the right.

根据牛顿第二定律，不平衡的力导致加速。箱子将向右加速。

The acceleration can be calculated using a = F / m = 50 N / 50 kg = 1 m/s².

加速度可以用 a = F / m = 50 N / 50 kg = 1 m/s² 计算。

If the push force were exactly 150 N, the resultant force would be zero, and the box would move at constant speed (or stay at rest if initially at rest).

如果推力恰好为150 N，合力为零，箱子将保持匀速直线运动（或原来静止则保持静止）。

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3. Case Study: Series Circuit Troubleshooting | 案例分析：串联电路故障排查

In a simple series circuit consisting of a battery, a switch and two identical light bulbs, you close the switch. One bulb lights up brightly, but the other remains completely dark. Explain possible causes and how to test each.

在一个由电池、开关和两个相同灯泡组成的简单串联电路中，闭合开关后，一个灯泡明亮发光，另一个完全不亮。解释可能的原因并说明如何排查。

In a series circuit, the current is the same everywhere. If one bulb is not lit, the circuit is still complete (otherwise both would be off). The dark bulb may be short-circuited, or its filament may be broken but is bypassed by a short. Another possibility is a loose connection inside the dark bulb holder that still allows current through the other bulb but not through the dark bulb’s filament – however, in a true series, a break should stop all current. Therefore, the most likely cause is a short circuit across the dark bulb.

在串联电路中，各处电流相等。如果一个灯泡不亮，电路仍然是通路（否则两个都会熄灭）。不亮的灯泡可能被短路，或者其灯丝断裂但被短路导线绕过。另一种可能是灯座内部接触不良，但这通常会中断电流。最可能的原因是不亮的灯泡两端发生了短路。

Troubleshooting: swap the bulbs. If the same bulb remains dark in the new position, the bulb itself is faulty (internally shorted or open). If the previously bright bulb now becomes dark, the fault is in the socket or wiring of that position (a short circuit). A short circuit provides an easy path for current, bypassing the bulb filament.

排查方法：交换两个灯泡。如果同一个灯泡在新位置仍不亮，说明灯泡本身有故障（内部短路或断路）。如果原来亮的灯泡现在不亮了，说明该灯座或连线存在短路

Published by TutorHao | Year 7 Physics Revision Series | aleveler.com

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