Dynamics
Balanced and unbalanced forces, action–reaction pairs, one-dimensional free-body diagrams, F = ma and friction.
Learning goals
- Describe the effect of balanced and unbalanced forces on a body
- Describe ways a force may change motion
- Identify action–reaction pairs on interacting bodies
- Draw free-body diagrams for one-dimensional force systems
- Apply resultant force = mass × acceleration
- Explain the effects of friction on motion
G2 Science (Physics) · Topic 4
Read the complete lesson from top to bottom first. Pause for its examples and independent questions, then use a short topic check to decide what to practise again.
Before you begin
Build the idea in order
- Forces on one body
- Resultant force
- F = ma
- Friction and force pairs
Lessons
Dynamics
Balanced and unbalanced forces, action–reaction pairs, one-dimensional free-body diagrams, F = ma and friction.
Check your understanding
Dynamics topic check
Check the required topic capabilities and get focused practice for ideas that need another look.
What to remember
- Zero resultant force means zero acceleration.
- Use F = ma with the resultant force.
- A free-body diagram shows only forces on the named body.
- Action–reaction forces act on different bodies.
- Friction opposes relative motion or its tendency.
Topic and syllabus information
Dynamics is Topic 4 in K223 / K224 Physics component · 2027.
The lesson stays within G2 depth and includes the explanations, examples and practice needed for this topic.
Reviewed 9 Aug 2026
Continue with the next resource in this course.
Course and syllabus information
- Course
- SEC G2 Science Physics component
- Edition
- SEC G2 Science Physics component 2027