SEC G3 Combined Science Physics component K326/K327
CP2: Kinematics
Connect speed, velocity, acceleration, distance-time graphs, and speed-time graphs within one-direction motion.
Reviewed for the 2027 cohort on 19 July 2026. The official syllabus remains authoritative for assessable wording and paper details.
Core notes
Kinematics turns a changing position into quantities and graphs that describe how fast an object moves and how its velocity changes.
Speed, velocity, and acceleration
Speed compares distance with time, while velocity is speed in a stated direction. Average speed uses the total distance and the full elapsed time, including stops.
Uniform acceleration gives equal changes in velocity in equal time intervals. If that rate changes, the acceleration is non-uniform and a single constant value cannot describe the whole interval.
Reading and plotting motion graphs
On a distance-time graph, gradient represents speed. A horizontal segment shows rest, a straight sloping segment shows uniform speed, and a changing gradient shows non-uniform speed.
On a speed-time graph, height gives speed and gradient gives acceleration. Rest lies on the time axis, constant speed is horizontal above it, and a curve indicates non-uniform acceleration. Plot time horizontally and label both axes with quantity and unit.
Area and free fall
For one-direction motion with uniform speed or acceleration, the area between a speed-time graph and the time axis gives the distance travelled. Split a compound region into rectangles and triangles when needed.
Near Earth, free fall is modelled with an approximately constant acceleration of . State when the model ignores air resistance.
Formulae and relationships
| Relationship | Use |
|---|---|
| Find average speed for a complete journey. | |
| Find uniform acceleration. |
Worked examples
Example 1: A runner increases speed uniformly from to in . Find the acceleration and distance.
- Use the velocity change: .
- Divide by to obtain .
- Use the trapezium area: .
Answer: Acceleration ; distance .
Chapter checkpoint
Use these three moves to organise the topic before attempting a mixed or practical question.
- Distinguish speed from velocity and identify whether acceleration is uniform or non-uniform.
- Read gradient and area from one-direction distance-time and speed-time graphs with physical units attached.
- Use the free-fall value only when the near-Earth constant-acceleration model is appropriate.
Official outcome coverage
K326 CP2: 9 mapped outcomes, references CP2(a), CP2(b), CP2(c), CP2(d), CP2(e), CP2(f), CP2(g), CP2(h), CP2(i). Check the official K326 syllabus.
K327 CP2: 9 mapped outcomes, references CP2(a), CP2(b), CP2(c), CP2(d), CP2(e), CP2(f), CP2(g), CP2(h), CP2(i). Check the official K327 syllabus.
The outcome wording is not reproduced here. The relevant official syllabus remains authoritative for exact assessable scope.
Practical and data connection
Determine acceleration of free fall from measured distance and time data. State the independent and dependent variables, repeat timings, plot the required motion graph, use its gradient or area with units, and explain how timing resolution or release inconsistency affects the result.
Exam traps and retrieval check
Avoid these traps
- Using moving time instead of total journey time for average speed.
- Reading graph height when the question asks for gradient.
- Forgetting that speed-time area represents distance.
Check from memory
What does a flat distance-time segment mean?
The object is stationary.
What does speed-time gradient measure?
Acceleration.
What near-Earth free-fall value is used?
Approximately .
Official Combined Science scope
This shared Combined Physics owner serves both K326 and K327. Speed, velocity, acceleration, one-direction motion graphs, graph area, and near-Earth free fall.