Centripetal acceleration
Cambridge A-Level Physics (9702) · Unit 12: Motion in a circle · 8 flashcards
Centripetal acceleration is topic 12.2 in the Cambridge A-Level Physics (9702) syllabus , positioned in Unit 12 — Motion in a circle , alongside Kinematics of uniform circular motion. In one line: A force of constant magnitude that is always perpendicular to the direction of motion is required. This force continuously changes the object's direction without changing its speed, resulting in centripetal acceleration.
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 8 flashcards — 1 definition, 2 key concepts and 5 calculations — covering the precise wording mark schemes reward. Use the definition card 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.
What condition regarding force is necessary for centripetal acceleration
A force of constant magnitude that is always perpendicular to the direction of motion is required. This force continuously changes the object's direction without changing its speed, resulting in centripetal acceleration.
What the Cambridge 9702 syllabus says
Official 2025-2027 spec · A2 LevelThese are the exact learning outcomes Cambridge sets for this topic. The candidate is expected to be able to do each of these on the relevant paper.
- understand that a force of constant magnitude that is always perpendicular to the direction of motion causes centripetal acceleration
- understand that centripetal acceleration causes circular motion with a constant angular speed
- recall and use a = rω2 and a = v2 / r
- recall and use F = mrω2 and F = mv2 / r
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.
What condition regarding force is necessary for centripetal acceleration?
A force of constant magnitude that is always perpendicular to the direction of motion is required. This force continuously changes the object's direction without changing its speed, resulting in centripetal acceleration.
How does centripetal acceleration relate to circular motion and angular speed?
Centripetal acceleration causes circular motion with a constant angular speed. The acceleration continuously changes the velocity's direction, maintaining a constant radius and consistent rate of rotation.
State the formula relating centripetal acceleration (a) to radius (r) and angular speed (ω).
The relationship is given by the formula: a = rω²
State the formula relating centripetal acceleration (a) to velocity (v) and radius (r).
The relationship is given by the formula: a = v²/r
State the formula relating centripetal force (F) to mass (m), radius (r), and angular speed (ω).
The relationship is given by the formula: F = mrω²
State the formula relating centripetal force (F) to mass (m), velocity (v), and radius (r).
The relationship is given by the formula: F = mv²/r
Explain how centripetal force affects the speed of an object moving in a circle.
Centripetal force does NOT change the speed of an object. Since the force is always perpendicular to the motion, no work is done (W=F.d), hence, kinetic energy and speed remain constant. The force only changes the direction.
A 0.5 kg mass is rotating in a circle of radius 1.0 m with a speed of 2.0 m/s. Calculate the centripetal force.
Using F = mv²/r, the centripetal force is F = (0.5 kg) * (2.0 m/s)² / (1.0 m) = 2.0 N
Review the material
Read full revision notes on Centripetal acceleration — definitions, equations, common mistakes, and exam tips.
Read NotesMore topics in Unit 12 — Motion in a circle
Centripetal acceleration 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 Centripetal acceleration 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.
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