Year 9 CAIE Physics: Unit Test Mock Paper Analysis | Year 9 CAIE 物理：单元测试模拟卷解析

📚 Year 9 CAIE Physics: Unit Test Mock Paper Analysis | Year 9 CAIE 物理：单元测试模拟卷解析

This article provides a detailed walkthrough of a Year 9 CAIE Physics unit test mock paper. Each question is analysed with clear explanations and model answers to help students review key concepts and exam techniques.

本文详细解析了一份针对 Year 9 CAIE 物理单元测试的模拟试卷。每个问题都附有清晰的解答和模型答案，帮助学生复习关键概念和考试技巧。

1. Speed Calculation | 速度计算

Question: A cyclist travels 600 metres in 120 seconds. Calculate the cyclist’s average speed in metres per second (m/s).

题目：一名骑自行车的人在120秒内行驶了600米。计算其平均速度，单位为米每秒（m/s）。

Answer and Explanation: The formula for average speed is speed = distance / time. Substitute the given values: speed = 600 m / 120 s = 5 m/s. Always include the correct unit. The cyclist covers 5 metres each second on average.

答案与解析：平均速度的公式为速度 = 距离 ÷ 时间。代入已知数值：速度 = 600 m ÷ 120 s = 5 m/s。永远要写出正确的单位。骑行者平均每秒前进5米。

2. Density of a Regular Solid | 规则固体的密度

Question: A metal block has a mass of 300 g and a volume of 25 cm³. Calculate its density in g/cm³ and in kg/m³.

题目：一个金属块的质量为300克，体积为25立方厘米。计算它的密度，单位分别用克每立方厘米和千克每立方米表示。

Answer and Explanation: Density = mass / volume. In g/cm³: density = 300 g / 25 cm³ = 12 g/cm³. To convert to kg/m³, note that 1 g/cm³ = 1000 kg/m³, so 12 g/cm³ = 12 × 1000 = 12,000 kg/m³. Alternatively, convert mass to 0.3 kg and volume to 2.5 × 10⁻⁵ m³, then density = 0.3 / (2.5×10⁻⁵) = 12,000 kg/m³. This is a dense metal such as lead.

答案与解析：密度 = 质量 ÷ 体积。在g/cm³单位下：密度 = 300 g ÷ 25 cm³ = 12 g/cm³。换算为kg/m³时，记住1 g/cm³ = 1000 kg/m³，因此12 g/cm³ = 12 × 1000 = 12,000 kg/m³。也可以将质量转换为0.3 kg，体积转换为2.5 × 10⁻⁵ m³，再计算密度 = 0.3 ÷ (2.5×10⁻⁵) = 12,000 kg/m³。这种密度接近铅等重金属。

3. Balanced and Unbalanced Forces | 平衡力与非平衡力

Question: A box is pushed to the right across a horizontal surface with a force of 10 N. Friction opposing the motion is 4 N. Determine the resultant force acting on the box and its direction.

题目：一个盒子在水平面上被向右推，推力为10 N。阻碍运动的摩擦力为4 N。求作用在盒子上的合力及其方向。

Answer and Explanation: The resultant force is the vector sum of all forces. Here, the forces along the same line can be subtracted: 10 N (right) – 4 N (left) = 6 N to the right. Because the net force is not zero, the forces are unbalanced and the box will accelerate to the right according to Newton’s second law.

答案与解析：合力是所有力的矢量和。这里，同一直线上的力可以相减：10 N（右）- 4 N（左）= 6 N，方向向右。由于合力不为零，力是不平衡的，根据牛顿第二定律，盒子将向右加速。

4. Energy Transfers in a Light Bulb | 灯泡中的能量转化

Question: Describe the energy transfers that occur when a battery-powered light bulb is switched on. Identify the useful output energy and the wasted energy.

题目：描述当电池供电的灯泡打开时发生的能量转化。指出有用的输出能量和浪费的能量。

Answer and Explanation: The chemical energy stored in the battery is converted into electrical energy in the circuit. The bulb filament then transforms most of this electrical energy into thermal (internal) energy and some into light energy. The useful output is light energy; the heat energy is wasted because it is not the desired form. In an LED bulb, the proportion of light is higher, but heat is still produced.

答案与解析：电池中储存的化学能转化为电路中的电能。灯丝再将大部分电能转化为热能（内能），一部分转化为光能。有用的输出是光能；热能被浪费，因为它不是我们希望的形式。在LED灯泡中，光的比例更高，但仍会产生一些热量。Published by TutorHao | Year 9 Physics Revision Series | aleveler.com

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