Circular Motion
An object moving in a circle at constant speed is always accelerating towards the centre because its direction keeps changing.
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An object moving in a circle at constant speed is always accelerating towards the centre because its direction keeps changing.
- A centripetal force points to the centre
- Speed can be constant while velocity changes
- Greater speed needs a greater force
🧠 Quick quiz
Three questions. Score 2 or more to complete the topic.
What is Circular Motion?
Within Physics, which covers forces, energy, waves, electricity, magnetism, light and space explained through motion and experiments, this topic explains Circular Motion. Physics topics explain how things move, push, heat up and carry energy, so each one here pairs a definition with a live model you can change.
Check that you can explain Circular Motion in your own words and give one example from everyday life. If you can do that, you have understood the core idea.
Understanding Circular Motion explains how the physical world behaves, from sport and transport to electricity and medicine.
Circular Motion in detail
An object moving in a circle at constant speed is continuously accelerating, because its velocity changes direction. The acceleration points toward the centre and is called centripetal acceleration, a = v²/r, and the resultant force toward the centre is the centripetal force F = mv²/r.
The centripetal force is not a separate force but is provided by something real: tension in a string, friction on tyres, gravity for a satellite. If the force disappears, the object moves off along a straight tangent. Circular motion explains cars on bends, loops in roller coasters and planetary orbits.
How the interactive helps you understand Circular Motion
Watch the orbit in the interactive. Use any sliders or buttons it offers to change the values and see how the orbit responds.
Before you change anything, predict the result. Then change one value at a time and check whether your prediction was right. This is a quick way to build a correct mental model of Circular Motion.
Real-life uses and examples
- Predict what a ball, car or circuit will do with Circular Motion before you do the calculation.
- Explain everyday devices, such as brakes, lifts or chargers, using Circular Motion.
- Use Circular Motion to make sense of a practical and its results.
Common mistakes to avoid
- Mixing up Circular Motion with a related quantity that has different units.
- Forgetting that some quantities, such as force or velocity, also have a direction.
- Learning the definition without testing it. Use the quiz and the interactive to check that you can apply the idea.
Frequently asked questions about Circular Motion
What is Circular Motion?
An object moving in a circle at constant speed is always accelerating towards the centre because its direction keeps changing.
What are the most important points about Circular Motion?
The main points are: A centripetal force points to the centre; Speed can be constant while velocity changes; Greater speed needs a greater force.
Why is Circular Motion useful?
Understanding Circular Motion explains how the physical world behaves, from sport and transport to electricity and medicine.
How can I practise Circular Motion?
Open the interactive at the top of this page and change the controls one at a time. Predict the result before each change, then take the three-question quiz. A score of two or more marks the topic as complete on this device.
Which topics are related to Circular Motion?
Related topics in Physics include States of Matter and Changes, Latent Heat, Thermal Radiation.