Physics 12 · Physics · Lesson 3.1
Uniform circular motion
- Level
- Grade 12
- Reading time
- 11 min reading
- Review
- Last reviewed 2026-09-03
- Standard
- Accuracy standard
- Errata
Abstract
Centripetal force.
What is centripetal force?
Short answer
Centripetal force is the net inward force that keeps an object moving along a circular path, always directed toward the centre of the circle. Its magnitude is F = mv²/r, where m is mass, v is speed, and r is the radius. It is not a new kind of force — gravity, tension, or friction can each act as the centripetal force in a given situation.
Concept preview
What you will be able to do
- 01Explain why circular motion requires a centripetal (centre-seeking) force
- 02Calculate centripetal acceleration and force
- 03Identify the real force providing the centripetal force in each situation
Swing a ball on a string in a steady circle. Its speed is constant, yet it is accelerating every instant — because velocity is a vector, and the direction of the velocity is forever changing. This is the mind-bending heart of uniform circular motion: constant speed, but never-constant velocity, and therefore a continuous acceleration even though nothing speeds up or slows down.
School Plan
Uniform circular motion
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Related topics
Frequently asked questions
- Is centripetal force a separate force?
- No. It is the name for whatever net inward force causes circular motion — often gravity, tension, or friction.
- What is centrifugal force?
- An apparent outward force felt in a rotating frame; it is not a real force acting on the object in an inertial frame.