Uniform Circular Motion
Circular motion at constant speed still has acceleration toward the center.
About this topic
An object moving in a circle at constant speed is still accelerating because its direction keeps changing. This centripetal acceleration points toward the centre and has magnitude a = v²/r = ω²r.
The period T is the time for one revolution, so v = 2πr/T. The net inward force, F = mv²/r, is supplied by tension, friction, gravity or a normal force depending on the situation. The angular speed ω = 2π/T is measured in radians per second.
Example: a 0.5 kg ball on a 1 m string whirled at 4 m/s has a = 16 m/s² inward and needs a tension of 8 N. A car rounding a bend relies on friction between tyres and road, and a satellite relies on gravity. Washing machines, roller coaster loops and centrifuges all use circular motion.
Misconceptions: there is no outward force pulling the object away; the feeling of being thrown outward is inertia, as your body tries to continue in a straight line. If the string breaks, the ball flies off along a tangent, not radially outward.
Key ideas
- Velocity direction keeps changing
- a = v²/r points to the center
- Period T = 2πr/v
Quick check
Use cases: where Uniform Circular Motion helps
- Homework: review the key idea behind Uniform Circular Motion before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Uniform Circular Motion without notes.
- Visual learning: play with the interactive lab to see how Uniform Circular Motion changes when you adjust its inputs.
- Teaching a friend: explain Uniform Circular Motion in your own words, then compare your version with the key ideas.
The same laws describe car crashes, sports, satellites and everyday machines.
Frequently asked questions
What is Uniform Circular Motion?
Circular motion at constant speed still has acceleration toward the center.
What will I learn in Uniform Circular Motion?
Velocity direction keeps changing. a = v²/r points to the center. Period T = 2πr/v.
Is Uniform Circular Motion part of Physics?
Yes. It is one of 150 Physics topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Uniform Circular Motion lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Uniform Circular Motion?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.