📚 Common Misconceptions and Corrections in Year 11 WJEC Physics | Year 11 WJEC 物理常见误区与纠正方法
In Year 11 WJEC Physics, students often develop intuitive but incorrect ideas about forces, energy, electricity, waves and radioactivity. These misconceptions can hinder deeper understanding and problem-solving. This article identifies the most common pitfalls and provides clear corrections to help you master the syllabus.
在学习Year 11 WJEC 物理时，学生常会产生一些看似合理但实际错误的观念，涵盖力、能量、电学、波和放射性等主题。这些误区会妨碍深入理解和解题。本文列举最常见的误区并提供清晰的纠正方法，助你掌握课程内容。
1. Constant Force Is Required for Constant Motion | 匀速运动需要恒力维持
Many learners believe that a constant driving force must be applied to keep an object moving at a steady speed. This idea originates from daily experiences with friction. For example, a car needs a continuous engine force to cruise on a motorway.
许多学生认为要保持物体匀速运动必须施加恒定的驱动力。这种观念源于日常摩擦力的体验，例如汽车在高速公路上巡航需要发动机持续提供动力。
In physics, Newton's First Law states that an object continues at constant velocity unless a net external force acts on it. The car's engine force balances air resistance and friction, so the net force is zero — the car is not accelerating. In space, far from any forces, a probe moves at constant velocity without any thrust. Constant motion does not require a net force; it requires zero net force.
物理学中，牛顿第一定律指出，除非受到净外力，物体将保持匀速直线运动。汽车的发动机力平衡了空气阻力和摩擦力，因此净力为零——汽车没有加速。在太空中远离任何力的探测器无需推力就能匀速运动。匀速运动不需要净力，而是需要净力为零。
The misconception arises because we often overlook the balancing forces. Training yourself to identify all forces and calculate the resultant force will eliminate the error.
这种误区源于我们经常忽视平衡力。训练自己识别所有力并计算合力能消除这一错误。
2. Heavier Objects Fall Faster | 物体越重下落越快
A common belief is that a heavy brick hits the ground before a light tennis ball when dropped from the same height. In everyday air resistance, this may appear true, but it violates the principle of free fall.
常见的想法是，从同一高度释放，重砖块比轻网球先落地。在存在空气阻力的日常情况下这似乎成立，但这违背了自由落体原理。
all objects experience the same gravitational field strength g (9.8 m/s² on Earth). Newton' law gives acceleration a = F/m. For weight, F = mg, so a = mg/m = g, independent of mass.
在没有空气阻力时，所有物体都受到相同的重力场强度 g（地球为9.8 m/s²）。牛顿第二定律给出加速度 a = F/m。对于重力，F = mg，所以 a = mg/m = g，与质量无关。
a = g
Galileo's thought experiment and the Apollo 15 hammer-feather drop on the Moon confirmed this. Thus, neglecting air resistance, all objects fall with the same acceleration. Always state 'air resistance ignored' when applying this principle in WJEC exams.
伽利略的思想实验和阿波罗15号在月球上的锤子羽毛下落实验证实了这一点。因此，忽略空气阻力，所有物体以相同加速度下落。在WJEC考试中应用这一原理时务必注明“忽略空气阻力”。
3. Action and Reaction Cancel Each Other | 作用力与反作用力相互抵消
Students often pair Newton's Third Law force pairs and conclude that they cancel out, leading to no motion. For instance, a book resting on a table experiences a downward weight and an upward normal force; these are often mistakenly called action-reaction.
学生常常将牛顿第三定律的力对配对，并得出结论这些力相互抵消，导致物体无法运动。例如，放在桌子上的书受到向下的重力和向上的支持力；这些常被误称为作用力与反作用力。
Actually, action-reaction pairs act on different bodies. The weight is the Earth pulling the book down; its reaction is the book pulling the Earth up. The normal force is the table pushing the book up; its reaction is the book pushing the table down. Since the forces act on different objects, they do not cancel in the free-body diagram of a single object. The book remains at rest because the net force on the book is zero (weight and normal balance, but they are not an action-reaction pair).
实际上，作用力与反作用力作用在不同物体上。重力是地球向下拉书；其反作用是书向上拉地球。支持力是桌子向上推书；其反作用是书向下推桌子。由于这些力作用在不同物体上，它们不会在单个物体的受力分析中抵消。书静止是因为书所受净力为零（重力与支持力平衡，但它们不是作用力-反作用力对）。
Remember: for two forces to cancel, they must act on the same object and be equal and opposite. Third-law pairs never act on the same object.
记住：两个力要抵消，必须
Published by TutorHao | Year 11 Physics Revision Series | aleveler.com
更多咨询请联系16621398022（同微信）
或截图后用「扫一扫 → 相册」选择本图