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

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

Welcome to our case study practical drills for Year 7 OCR Physics. These exercises will help you apply scientific concepts to real-world scenarios, a key skill for your exams. Each case presents a situation, followed by questions and detailed analysis. Let’s dive in and practise your physics thinking!

欢迎来到 Year 7 OCR 物理案例分析实战演练。这些练习将帮助你运用科学概念解决真实情境问题，这是考试中非常关键的能力。每个案例都会提供一种场景，随后提出问题和详细分析。让我们开始锻炼你的物理思维吧！

1. Pushing a Box: Balanced and Unbalanced Forces | 推箱子：平衡力与不平衡力

Imagine a student trying to push a heavy box on the floor. She pushes with a small force, but the box stays still. The reason is that the static friction force between the box and the floor acts in the opposite direction and balances her push. These forces are balanced, so there is no change in motion.

设想一名学生试图推动地上的重箱子。她用较小的力推，箱子却纹丝不动。这是因为箱子与地面之间的静摩擦力方向与推力相反，与之平衡。此时力是平衡的，因此运动状态不变。

When she increases the pushing force, it eventually overcomes the maximum static friction. The forces become unbalanced, causing the box to accelerate. Once moving, the friction changes to sliding friction, which is usually smaller than maximum static friction. If the push then balances sliding friction, the box can move at a steady speed.

当她加大推力时，外力最终会超过最大静摩擦力。力变得不平衡，箱子便开始加速。运动之后，摩擦力转变为滑动摩擦力，通常小于最大静摩擦力。如果推力与滑动摩擦力平衡，箱子就能保持匀速运动。

Key forces acting: applied push, friction, weight, and normal reaction force. A free-body diagram can help you visualise the directions.

作用的主要力包括：推力、摩擦力、重力和支持力。用受力示意图可以帮助你想象这些力的方向。

2. Weight and Mass on the Moon | 月球上的重量和质量

An astronaut has a mass of 60 kg on Earth. On Earth, weight = mass × gravitational field strength (about 10 N/kg), so her weight is 600 N. When she travels to the Moon, her mass remains 60 kg because mass is the amount of matter, which does not change with location.

一名宇航员在地球上的质量为60千克。在地球上，重量 = 质量 × 重力场强度（约10牛/千克），因此她的重量为600牛。当她来到月球，其质量仍为60千克，因为质量是物体所含物质的多少，不随地点改变。

On the Moon, the gravitational field strength is much weaker, about 1.6 N/kg. So her weight becomes 60 kg × 1.6 N/kg = 96 N (approximately 100 N). She feels much lighter because the pull of gravity is smaller.

月球上的重力场强度弱得多，约为1.6牛/千克。因此她的重量

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

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