Ever wondered why you feel pushed outward when going around...
Physics234 views·Updated 26 Jul 2026·2 pagesUnderstanding Circular Motion: Forces in Action
Jess@jess_eqxp
1
of 2
Understanding Radians and Angular Motion
Forget what you think you know about measuring angles - radians are actually much more useful than degrees in physics. A radian is simply the angle you get when the arc length equals the radius of the circle.
The formula is dead simple: angle = arc length ÷ radius. For one complete revolution, you always get 2π radians (about 6.28), which equals 360 degrees. To convert between them, just remember: multiply radians by 180/π to get degrees, or multiply degrees by π/180 to get radians.
Here's the key insight about circular motion: even when an object moves at constant speed around a circle, its velocity is constantly changing because direction keeps shifting. This means there's always acceleration happening, which requires a force - the centripetal force - pointing toward the centre.
Quick Tip: Think of centripetal as "centre-seeking" - it always pulls inward, never outward!
Angular velocity (ω) measures how fast the angle changes, whilst linear velocity measures the actual speed around the circle. They're connected by the simple relationship: v = ωr.
2
of 2
Calculating Centripetal Force
The magic formula for centripetal force is F = mv²/r, where m is mass, v is speed, and r is the radius. This force isn't some mysterious new force - it's just whatever forces (tension, gravity, friction) happen to be pulling the object toward the centre.
Let's tackle a real example: a 100g mass swinging on a 0.8m string at 10 Hz. First, find the speed: circumference = 2πr = 5.03m, so speed = 5.03 × 10 = 50.3 m/s. Then apply the formula: F = (0.1 × 50.3²) ÷ 0.8 = 316N of tension in the string.
You can also write centripetal force as F = mω²r when you know the angular velocity instead of linear velocity. Both formulas give the same answer - use whichever makes your calculation easier.
Remember: The centripetal force always points inward toward the centre, never outward. What you feel pushing you outward in a car is your body's inertia wanting to travel straight!
The period (T) and frequency are related by T = 1/f, and angular velocity connects to both: ω = 2π/T = 2πf.
We thought you’d never ask...
Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
You can download the app from Google Play Store and Apple App Store.
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
Similar content
Most popular content: Circular Motion
1Most popular content in Physics
9G
PhysicsGCSE Physics - Energy stores and Systems
Pl-Energy topic to revise for GCSE
111,3802
C
PhysicsConservation of energy- energy types and stores
Build a strong foundation in physics with these easy flashcards covering key concepts and principles.
96411
PhysicsForces and Motion Overview
Explore key concepts in Forces and Motion, including Hooke's Law, velocity, acceleration, and the principles of moments. This summary covers essential topics such as the relationship between force and extension, terminal velocity, and the impact of safety devices in physics. Ideal for AQA Physics Unit 5 revision.
109,214872
P
PhysicsPhysics Made Easy: Essential Concepts for Grade 10 Students
Master the fundamentals of physics with this comprehensive flashcard set designed specifically for grade 10 students. Learn key concepts and principles in an easy and engaging way!
104571
PhysicsPhysics paper 2 notes
physics aqa gcse paper 2 combined higher notes
111,24611
PhysicsPhysics Paper 2 Essentials
Master key concepts for AQA Combined Physics Paper 2, including electromagnetic waves, mechanics, forces, and motion. This comprehensive summary covers essential topics like wave properties, Newton's laws, and the motor effect, ensuring you're well-prepared for your exam.
1116,077941
PhysicsGCSE Physics Practical Experiments
Explore essential GCSE Physics practicals for AQA, covering key concepts such as Hooke's Law, wave properties, thermal insulation, and electrical circuits. This comprehensive guide includes step-by-step procedures, variables, and safety considerations for each experiment, ensuring a thorough understanding of practical applications in physics.
1111,416477
I
PhysicsIdentifying Types of Energy Stores
Learn to recognize different energy stores including kinetic, gravitational potential, chemical, and thermal in various objects and systems.
102380
Physicsphysics paper 2 foundation notes
aqa combined science physics paper 2 foundation notes
111,33138
Most popular content
9
SociologySociology of Education Overview
Explore comprehensive A-Level Sociology notes on the education system, covering key theories, policies, and sociological perspectives. This resource includes insights on marketisation, gender roles, cultural deprivation, and educational inequalities, providing a thorough understanding of how education shapes social stratification and individual achievement. Ideal for exam preparation and in-depth study.
12102,9683,040
SociologySociology of Families: Comprehensive Revision
Dive into an extensive overview of family dynamics, perspectives, and patterns in sociology. This resource covers key concepts such as family diversity, gender roles, marriage, and the impact of social policies on family structures. Perfect for A-Level Sociology students preparing for Paper 2.
1273,7782,306
CriminologyCriminology: Crime & Punishment Overview
Comprehensive mindmaps covering key concepts in the Crime and Punishment topic for WJEC Criminology Unit 4. This resource includes detailed insights into the Criminal Justice System, crime prevention strategies, sentencing models, and the roles of various agencies. Ideal for A-Level revision, ensuring you grasp essential theories and legislative processes to excel in your exams.
1254,8971,060
SociologyComprehensive Crime & Deviance Overview
Explore an extensive revision of crime and deviance topics, including theories, types of crime, and the impact of media. This resource covers key concepts such as Marxism, functionalism, gender and crime, and the influence of globalization on criminal behavior. Ideal for students seeking a thorough understanding of criminology and its various theories. Type: Full Topic Revision.
1251,6701,400
C
BiologyCell Biology and Cell structure
cell structures
113,2880
T
BiologyThe functions of subcellular structures - B1 Biology
Flashcards on the different functions of subcellular structures: cell membrane, nucleus, mitochondria, ribosomes, cytoplasm, permant vacuole, chloroplasts and cell wall.
112,8215
SociologySociological Theories Overview
Comprehensive revision of key sociological theories including Functionalism, Marxism, Feminism, and Interpretivism. Explore concepts like value freedom, identity formation, and the critique of social control. Ideal for AQA A-Level Sociology students preparing for exams. This summary covers essential theories and their implications in sociology, providing a clear understanding of each perspective.
1231,483846
CriminologyWJEC Unit 4 Criminology
Criminology unit 4 detailed revision note
127,177125
1
Biology1.cells Gcse biology question cards
combined science higher biology
112,3694
Students love us — and so will you.
4.6/5App Store
4.7/5Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan SiOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha KlichAndroid user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
AnnaiOS user
Physics234 views·Updated 26 Jul 2026·2 pagesUnderstanding Circular Motion: Forces in Action
Jess@jess_eqxp
Ever wondered why you feel pushed outward when going around a sharp corner in a car? That's circular motion in action! Understanding how objects move in circles is crucial for explaining everything from planets orbiting the sun to the physics...
1
of 2
Sign up to see the content. It's free!
- Access to all documents
- Improve your grades
- Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Understanding Radians and Angular Motion
Forget what you think you know about measuring angles - radians are actually much more useful than degrees in physics. A radian is simply the angle you get when the arc length equals the radius of the circle.
The formula is dead simple: angle = arc length ÷ radius. For one complete revolution, you always get 2π radians (about 6.28), which equals 360 degrees. To convert between them, just remember: multiply radians by 180/π to get degrees, or multiply degrees by π/180 to get radians.
Here's the key insight about circular motion: even when an object moves at constant speed around a circle, its velocity is constantly changing because direction keeps shifting. This means there's always acceleration happening, which requires a force - the centripetal force - pointing toward the centre.
Quick Tip: Think of centripetal as "centre-seeking" - it always pulls inward, never outward!
Angular velocity (ω) measures how fast the angle changes, whilst linear velocity measures the actual speed around the circle. They're connected by the simple relationship: v = ωr.
2
of 2Sign up to see the content. It's free!
- Access to all documents
- Improve your grades
- Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Calculating Centripetal Force
The magic formula for centripetal force is F = mv²/r, where m is mass, v is speed, and r is the radius. This force isn't some mysterious new force - it's just whatever forces (tension, gravity, friction) happen to be pulling the object toward the centre.
Let's tackle a real example: a 100g mass swinging on a 0.8m string at 10 Hz. First, find the speed: circumference = 2πr = 5.03m, so speed = 5.03 × 10 = 50.3 m/s. Then apply the formula: F = (0.1 × 50.3²) ÷ 0.8 = 316N of tension in the string.
You can also write centripetal force as F = mω²r when you know the angular velocity instead of linear velocity. Both formulas give the same answer - use whichever makes your calculation easier.
Remember: The centripetal force always points inward toward the centre, never outward. What you feel pushing you outward in a car is your body's inertia wanting to travel straight!
The period (T) and frequency are related by T = 1/f, and angular velocity connects to both: ω = 2π/T = 2πf.
We thought you’d never ask...
Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
You can download the app from Google Play Store and Apple App Store.
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
Similar content
Most popular content: Circular Motion
1Most popular content in Physics
9G
PhysicsGCSE Physics - Energy stores and Systems
Pl-Energy topic to revise for GCSE
111,3802
C
PhysicsConservation of energy- energy types and stores
Build a strong foundation in physics with these easy flashcards covering key concepts and principles.
96411
PhysicsForces and Motion Overview
Explore key concepts in Forces and Motion, including Hooke's Law, velocity, acceleration, and the principles of moments. This summary covers essential topics such as the relationship between force and extension, terminal velocity, and the impact of safety devices in physics. Ideal for AQA Physics Unit 5 revision.
109,214872
P
PhysicsPhysics Made Easy: Essential Concepts for Grade 10 Students
Master the fundamentals of physics with this comprehensive flashcard set designed specifically for grade 10 students. Learn key concepts and principles in an easy and engaging way!
104571
PhysicsPhysics paper 2 notes
physics aqa gcse paper 2 combined higher notes
111,24611
PhysicsPhysics Paper 2 Essentials
Master key concepts for AQA Combined Physics Paper 2, including electromagnetic waves, mechanics, forces, and motion. This comprehensive summary covers essential topics like wave properties, Newton's laws, and the motor effect, ensuring you're well-prepared for your exam.
1116,077941
PhysicsGCSE Physics Practical Experiments
Explore essential GCSE Physics practicals for AQA, covering key concepts such as Hooke's Law, wave properties, thermal insulation, and electrical circuits. This comprehensive guide includes step-by-step procedures, variables, and safety considerations for each experiment, ensuring a thorough understanding of practical applications in physics.
1111,416477
I
PhysicsIdentifying Types of Energy Stores
Learn to recognize different energy stores including kinetic, gravitational potential, chemical, and thermal in various objects and systems.
102380
Physicsphysics paper 2 foundation notes
aqa combined science physics paper 2 foundation notes
111,33138
Most popular content
9SociologySociology of Education Overview
Explore comprehensive A-Level Sociology notes on the education system, covering key theories, policies, and sociological perspectives. This resource includes insights on marketisation, gender roles, cultural deprivation, and educational inequalities, providing a thorough understanding of how education shapes social stratification and individual achievement. Ideal for exam preparation and in-depth study.
12102,9683,040
SociologySociology of Families: Comprehensive Revision
Dive into an extensive overview of family dynamics, perspectives, and patterns in sociology. This resource covers key concepts such as family diversity, gender roles, marriage, and the impact of social policies on family structures. Perfect for A-Level Sociology students preparing for Paper 2.
1273,7782,306
CriminologyCriminology: Crime & Punishment Overview
Comprehensive mindmaps covering key concepts in the Crime and Punishment topic for WJEC Criminology Unit 4. This resource includes detailed insights into the Criminal Justice System, crime prevention strategies, sentencing models, and the roles of various agencies. Ideal for A-Level revision, ensuring you grasp essential theories and legislative processes to excel in your exams.
1254,8971,060
SociologyComprehensive Crime & Deviance Overview
Explore an extensive revision of crime and deviance topics, including theories, types of crime, and the impact of media. This resource covers key concepts such as Marxism, functionalism, gender and crime, and the influence of globalization on criminal behavior. Ideal for students seeking a thorough understanding of criminology and its various theories. Type: Full Topic Revision.
1251,6701,400
C
BiologyCell Biology and Cell structure
cell structures
113,2880
T
BiologyThe functions of subcellular structures - B1 Biology
Flashcards on the different functions of subcellular structures: cell membrane, nucleus, mitochondria, ribosomes, cytoplasm, permant vacuole, chloroplasts and cell wall.
112,8215
SociologySociological Theories Overview
Comprehensive revision of key sociological theories including Functionalism, Marxism, Feminism, and Interpretivism. Explore concepts like value freedom, identity formation, and the critique of social control. Ideal for AQA A-Level Sociology students preparing for exams. This summary covers essential theories and their implications in sociology, providing a clear understanding of each perspective.
1231,483846
CriminologyWJEC Unit 4 Criminology
Criminology unit 4 detailed revision note
127,177125
1
Biology1.cells Gcse biology question cards
combined science higher biology
112,3694
Students love us — and so will you.
4.6/5App Store
4.7/5Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan SiOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha KlichAndroid user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
AnnaiOS user