Fundamental Forces (A Level)
Key idea: An A Level extension: the four fundamental forces (gravitational, electromagnetic, strong and weak), with key properties and examples.
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The core idea
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Learning objectives
- Explore friction coefficients, variable-mass systems and the fundamental interactions beyond the H2 syllabus.
1. Definitions (Must Know)
In modern physics, interactions are grouped into four fundamental forces:
- Gravitational
- Electromagnetic
- Strong nuclear
- Weak nuclear
O Level vs A Level
For O Level (6091), you mainly use the simpler classification: contact forces vs non-contact forces (e.g. friction, tension, air resistance vs gravity, electrostatic, magnetic).
2. Key Ideas (What Earns Marks)
- Gravity: attractive, acts between masses, very long range.
- Electromagnetism: acts between charges and currents, can attract or repel, long range.
- Strong nuclear force: binds protons/neutrons in nuclei, very short range, strongest.
- Weak nuclear force: involved in certain radioactive decays, very short range.
3. Detailed Explanations
Summary table
| Force | What it acts on | Range | Can repel? | Examples |
|---|---|---|---|---|
| Gravitational | masses | infinite | No | weight, orbits |
| Electromagnetic | charges/currents | infinite | Yes | friction/contact forces (microscopic), electrostatics, magnetism |
| Strong nuclear | nucleons/quarks | very short | effectively attractive | holds nucleus together |
| Weak nuclear | particles in beta decay | very short | not usually described as “repel/attract” | beta decay |
4. Exam Tips
- If a question is about everyday forces (normal reaction, friction, tension), it’s usually enough to classify them as contact forces (even though their microscopic origin is electromagnetic).
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Course and syllabus information
- Course
- A-level H2 Physics topic extensions
- Syllabus scope
- Beyond the syllabus
- Edition
- A-level H2 Physics topic extensions