Kinematics of uniform circular motion
Cambridge A-Level Physics (9702) · Unit 12: Motion in a circle · 7 flashcards
Kinematics of uniform circular motion is topic 12.1 in the Cambridge A-Level Physics (9702) syllabus , positioned in Unit 12 — Motion in a circle , alongside Centripetal acceleration. In one line: A radian is the angle subtended at the center of a circle by an arc equal in length to the radius of the circle. There are 2π radians in a full circle.
Marked as A2 Level: examined at A Level in Paper 4 (A Level Structured Questions) and Paper 5 (Planning, Analysis and Evaluation). It is not tested on the AS-only papers (Papers 1, 2 and 3).
The deck below contains 7 flashcards — 3 definitions and 4 calculations — covering the precise wording mark schemes reward. Use the 3 definition cards to lock down command-word answers (define, state), then move on to the concept and calculation cards to handle explain, describe, calculate and compare questions.
The radian
A radian is the angle subtended at the center of a circle by an arc equal in length to the radius of the circle. There are 2π radians in a full circle.
What the Cambridge 9702 syllabus says
2025-2027 syllabus, in our words · A2 LevelWhat the syllabus expects you to be able to do in this topic, in plain English. For the exact wording, see the official syllabus (PDF).
- Define the radian, and give angular displacements in radians.
- Understand what angular speed means and use it in calculations.
- Recall v = rω and ω = 2π/T (T is the period), and use them in calculations.
Cambridge syllabus keywords to use in your answers
These are the official Cambridge 9702 terms tagged to this section. Mark schemes credit responses that use the exact term — weave them into your answers verbatim rather than paraphrasing.
Define the radian.
A radian is the angle subtended at the center of a circle by an arc equal in length to the radius of the circle. There are 2π radians in a full circle.
What is angular displacement?
Angular displacement (θ) is the angle, measured in radians, through which an object has turned about the centre of its circular path. For an arc length s on a circle of radius r, θ = s/r. At A Level it is treated as an angle, not a vector.
Define angular speed.
Angular speed (ω) is the rate of change of angular displacement. It is measured in radians per second (rad s⁻¹).
State the relationship between angular speed (ω) and period (T).
The angular speed is equal to 2π divided by the period: ω = 2π / T. This is derived from one full revolution (2π radians) in one period (T).
State the relationship between linear speed (v), radius (r), and angular speed (ω) for an object in uniform circular motion.
The linear speed is equal to the radius multiplied by the angular speed: v = rω. This means that for a given angular speed, objects at larger radii have greater linear speeds.
A particle moves in a circle of radius 0.2m with a period of 5s. What is its angular speed?
ω = 2π / T = 2π / 5 = 1.26 rad s⁻¹
A car travels around a circular track of radius 50m at a constant speed of 10 m/s. What is the car's angular speed?
Use v=rω and rearrange to get ω = v/r = 10/50 = 0.2 rad/s
Review the material
Read full revision notes on Kinematics of uniform circular motion — definitions, equations, common mistakes, and exam tips.
Read NotesMore topics in Unit 12 — Motion in a circle
Kinematics of uniform circular motion sits alongside these A-Level Physics decks in the same syllabus unit. Each uses the same spaced-repetition system, so progress in one informs the next.
Key terms covered in this Kinematics of uniform circular motion deck
Every term below is defined in the flashcards above. Use the list as a quick recall test before your exam — if you can't define one of these in your own words, flip back to that card.
How to study this Kinematics of uniform circular motion deck
Start in Study Mode, attempt each card before flipping, then rate Hard, Okay or Easy. Cards you rate Hard come back within a day; cards you rate Easy push out to weeks. Your progress is saved in your browser, so come back daily for 5–10 minute reviews until every card reads Mastered.
Study Mode
Rate each card Hard, Okay, or Easy after flipping.