📚 GCSE AQA Physics: Gravity – Key Points Revision | GCSE AQA 物理：万有引力 考点精讲
Gravity is a fundamental force that attracts objects with mass towards one another. On Earth, it gives weight to physical objects and causes the downward acceleration of free‑falling bodies. For GCSE AQA Physics, understanding gravity means distinguishing clearly between mass and weight, applying the weight equation, and explaining gravitational field strength in the context of different planets and moons.
引力是一种基本相互作用，有质量的物体彼此吸引。在地球上，引力赋予物体重量，并使自由落体产生向下的加速度。在 GCSE AQA 物理考试中，理解万有引力需要清楚区分质量与重量、运用重量计算公式，并结合不同行星和卫星解释引力场强度的概念。
1. What Is Gravity? | 什么是引力？
Gravity is a non‑contact force of attraction between two masses. The more massive the objects and the closer they are, the stronger the gravitational pull. On Earth, we experience gravity as the force that pulls everything towards the centre of the planet. This force causes objects to fall downwards, keeps the Moon in orbit around Earth, and holds the planets in orbit around the Sun.
引力是两个有质量的物体之间的一种非接触吸引力。物体的质量越大、距离越近，引力就越强。在地球上，我们感受到的引力是把一切拉向地心的力。这个力使物体向下掉落，让月球绕地球运转，并使行星绕太阳公转。
2. Mass and Weight Are Not the Same | 质量与重量不是一回事
Mass is the amount of matter in an object, measured in kilograms (kg). It is a scalar quantity and does not change wherever the object is located in the universe. Weight is the force acting on an object due to gravity, measured in newtons (N). Because weight is a force, it is a vector quantity and varies with the strength of the gravitational field.
质量是物体所含物质的多少，单位为千克（kg）。它是标量，无论物体在宇宙中何处，质量都不会改变。重量是重力作用于物体上的力，单位为牛顿（N）。由于重量是一种力，它是矢量，且随引力场强度的变化而变化。
3. Gravitational Field Strength | 引力场强度
Gravitational field strength (g) is the force per unit mass experienced by a small test mass placed in a gravitational field. It is measured in newtons per kilogram (N/kg). On the surface of Earth, g is approximately 9.8 N/kg, meaning a 1 kg mass experiences a gravitational force of about 9.8 N. Different planets have different gravitational field strengths: for example, on the Moon g is about 1.6 N/kg.
引力场强度（g）是放置在引力场中的小检验质量所受的力与其质量的比值。单位是牛顿每千克（N/kg）。在地球表面，g 约等于 9.8 N/kg，也就是说 1 kg 的物体会受到约 9.8 N 的引力。不同行星的引力场强度不同，例如月球表面的 g 约为 1.6 N/kg。
4. The Weight Equation | 重量计算公式
The relationship between weight, mass and gravitational field strength is given by the equation:
W = m × g
In this equation, W is weight in newtons (N), m is mass in kilograms (kg), and g is gravitational field strength in newtons per kilogram (N/kg). This formula shows that weight is directly proportional to both the mass of the object and the local gravitational field strength. If you know any two of these quantities, you can calculate the third.
重量、质量和引力场强度之间的关系由以下公式给出：
W = m × g
公式中，W 代表重量，单位为牛顿（N）；m 代表质量，单位为千克（kg）；g 代表引力场强度，单位为牛顿每千克（N/kg）。这个公式表明，重量与物体质量和当地引力场强度均成正比。已知任意两个量，便可计算第三个量。
5. Factors Affecting Gravitational Force | 影响引力的因素
The gravitational force between two objects depends on two factors: the masses of the objects and the distance between their centres. If either mass increases, the gravitational force increases. If the distance between centres increases, the force decreases rapidly – it follows an inverse square relationship. In everyday life, we see this effect most clearly when we compare weight on different planets or at different altitudes.
两物体间的引力大小取决于两个因素：物体的质量以及它们质心之间的距离。任何一个物体的质量增大，引力就增大；质心间距离增大，引力则迅速减小——遵循平方反比规律。在日常生活中，对比人在不同行星表面或不同海拔的体重，就能清楚地看到这种影响。
6. Gravity on Different Planets | 不同行星上的重力
Because each planet has its own mass and radius, the gravitational field strength varies significantly across the Solar System. On Jupiter, g ≈ 24.8 N/kg; on Mars, g ≈ 3.7 N/kg. This means that a 60 kg astronaut would weigh about 590 N on Earth, only about 96 N on the Moon, and over 1480 N on Jupiter. Mass stays the same, but weight changes dramatically.
由于每颗行星的质量和半径不同，太阳系内各处的引力场强度差异很大。木星表面 g ≈ 24.8 N/kg，火星表面 g ≈ 3.7 N/kg。这意味着一名 60 kg 的宇航员在地球上体重约为 590 N，在月球上仅为约 96 N，而在木星上则超过 1480 N。质量保持不变，但重量剧烈变化。
7. Gravity and Free Fall | 重力与自由落体
When the only force acting on an object is gravity, the object is said to be in free fall. In the absence of air resistance, all objects near Earth’s surface accelerate downwards at the same rate, regardless of their mass. This acceleration is the gravitational field strength, 9.8 m/s². In real life, air resistance opposes the motion, reducing the net acceleration.
当物体只受重力作用时，就称它处于自由落体状态。在没有空气阻力的情况下，地球表面附近的所有物体都以相同的加速度向下加速，而与它们的质量无关。这个加速度的大小就是引力场强度，约 9.8 m/s²。实际生活中，空气阻力会阻碍运动，减小合加速度。
8. Terminal Velocity and Air Resistance | 终端速度与空气阻力
When a falling object first starts moving, the only large force is its weight. As speed increases, air resistance (drag) builds up until it balances the weight. At this point, the resultant force is zero, acceleration stops, and the object falls at a constant speed called terminal velocity. This is a key example of how gravity, together with opposing forces, determines motion.
物体刚开始下落时，主要的力只有重力。随着速度增加，空气阻力（曳力）逐渐增大，直到与重力平衡。此时合力为零，加速度消失，物体便以恒定的速度下落，这个速度称为终端速度。这是说明重力与反作用力如何共同决定运动状态的典型例子。
9. Orbits and Universal Gravitation | 轨道运动与万有引力
Isaac Newton’s law of universal gravitation states that every particle attracts every other particle with a force proportional to the product of their masses and inversely proportional to the square of the distance between their centres. This force provides the centripetal force needed to keep planets in orbit around the Sun, satellites around Earth, and the Moon around Earth. The closer a satellite is to Earth, the faster it must travel to maintain its orbit.
牛顿的万有引力定律指出，任何两个质点都以一个与质量乘积成正比、与距离平方成反比的力互相吸引。这个力提供了行星绕太阳、卫星绕地球以及月球绕地球运转所需的向心力。卫星离地球越近，就必须以越大的速度运行才能维持轨道。
10. Measuring Weight and Mass Practically | 实际测量重量与质量
In the laboratory, mass is measured using a top‑pan balance or digital balance; weight is measured with a newton meter (spring balance). A spring balance works by measuring the extension of a spring, which is proportional to the force applied. When used on Earth, the scale is calibrated to read weight in newtons, but if the same spring balance were taken to the Moon, the weight reading would be lower because g is smaller.
在实验室中，质量用上盘天平或电子天平测量；重量用弹簧秤（牛顿计）测量。弹簧秤通过测量弹簧的伸长量来工作，伸长量与所受的力成正比。在地球上使用时，标尺被校准为读取以牛顿为单位的重量；但如果将同一个弹簧秤带到月球上，重量读数会因 g 较小而降低。
11. Common Exam Mistakes and How to Avoid Them | 常见考试错误与避免方法
One of the most common errors is confusing mass and weight. Remember: mass is in kilograms, never changes; weight is in newtons, depends on g. Another mistake is using the wrong value of g – always check the question’s context. Also, when substituting into W = m × g, ensure that mass is in kg, not in grams. Finally, draw clear force diagrams when discussing terminal velocity, showing weight and air resistance as balanced arrows.
最常见的错误之一是混淆质量与重量。要记住：质量单位为千克，从不改变；重量单位为牛顿，取决于 g。另一个错误是用错了 g 的值——一定要根据题目给出的情境确定。代入 W = m × g 时，要确保质量用千克而不是克。最后，讨论终端速度时要画出清晰的受力图，用平衡箭头表示重力和空气阻力。
12. Exam‑Style Quick Revision | 考点速记
- Mass: quantity of matter, kg, scalar, constant everywhere. / 质量：物质的多少，单位 kg，标量，处处不变。
- Weight: gravitational force, N, vector, varies with g. / 重量：重力，单位 N，矢量，随 g 变化。
- W = m × g: use correct units, g = 9.8 N/kg on Earth unless stated otherwise. / W = m × g：使用正确单位，地球上 g = 9.8 N/kg，除非题目另有说明。
- Free fall: all objects accelerate at g if no air resistance. / 自由落体：若无空气阻力，所有物体均以 g 加速。
- Terminal velocity: weight = air resistance, zero resultant force. / 终端速度：重力 = 空气阻力，合力为零。
- Orbits: gravity provides centripetal force; speed required depends on orbital radius. / 轨道运动：引力提供向心力；所需速率取决于轨道半径。
Keeping these core ideas at your fingertips will help you confidently tackle any gravity question in the AQA GCSE Physics exam.
把这些核心概念熟记于心，就能在 AQA GCSE 物理考试中自信应对任何有关引力的题目。
Published by TutorHao | GCSE AQA 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Cancel reply