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Emma Corden
28/09/2025
Physics
forces in action
455
•
28 Sept 2025
•
Newton's 2nd Law of Motion and Fun Physics Experiments for Class 9 and 11
Emma Corden
@emmacorden_rpll
1 / 8
Free Body Diagrams and Force Analysis
This page covers free body diagrams and provides examples of force analysis in various scenarios.
Key concepts:
- Free body diagrams use dots to represent objects and arrows to show forces.
- A detailed example of a helicopter lifting a mass is provided, demonstrating force calculations in different situations.
Highlight: When drawing free body diagrams, always use arrows to scale and a dot to represent the object.
Example: In the helicopter example, when the load experiences acceleration, the tension in the cable increases from 981N to 1081N.
Practical Investigation of Motion in Fluid
This page describes a practical investigation of motion in fluid and introduces forces on a slope.
Key points:
- The practical investigation involves dropping a ball bearing through a viscous fluid and measuring its motion.
- Forces on a slope are broken down into components parallel and perpendicular to the plane.
Vocabulary: Terminal velocity is the constant speed reached by an object falling through a fluid when the drag force equals the gravitational force.
Definition: The center of gravity is the point at which the entire weight of an object seems to act.
Moments and Force Analysis
This page introduces the concept of moments and provides examples of force analysis using trigonometry.
Key points:
- A moment is the product of force and the perpendicular distance from the pivot to the line of action of the force.
- The unit of moment is Newton-meter (Nm).
Definition: A moment is the turning effect of a force, calculated as the product of the force and the perpendicular distance from the pivot to the line of action of the force.
Example: For a force of 6N applied 0.1m from a pivot, the moment is 0.5 Nm.
The Principle of Moments and Force Couples
This page explains the principle of moments and introduces force couples and torques.
Key concepts:
- An object is in equilibrium when there is no net force acting on it and the sum of clockwise moments equals the sum of anticlockwise moments.
- Force couples consist of two equal and opposite forces acting in the same plane.
Definition: The principle of moments states that for an object in equilibrium, the sum of clockwise moments equals the sum of anticlockwise moments.
Vocabulary: A force couple consists of two equal and opposite forces acting in the same plane, creating a pure rotational effect.
Pressure in Fluids and Archimedes' Principle
This page covers pressure in fluids and introduces Archimedes' Principle.
Key points:
- Pressure in a fluid is calculated as P = F/A = mg/A = ρgh
- Archimedes' Principle states that the upthrust on a submerged object equals the weight of fluid displaced.
Definition: Archimedes' Principle states that the upthrust acting on a body submerged in a liquid is equal to the weight of the liquid that has been displaced.
Formula: Pressure in a fluid is given by P = ρgh, where ρ is density, g is gravitational acceleration, and h is depth.
Moments Practice Questions
This page provides practice questions on moments and their solutions.
Key points:
- Detailed solutions for moment calculations are provided, including trigonometric analysis.
- The principle of moments is applied to solve equilibrium problems.
Example: For a force of 5N applied at a 30° angle to a 0.2m lever arm, the moment is calculated as 5 × 0.1 = 0.5 Nm.
Highlight: When solving moment problems, always identify the perpendicular distance from the pivot to the line of action of the force.
Additional Moment Problems and Solutions
This page continues with more practice problems on moments and their detailed solutions.
Key points:
- A comprehensive problem involving a balanced beam is solved step-by-step.
- The principle of moments is restated and applied to find unknown weights and masses.
Example: In a balanced beam problem, the unknown weight is calculated to be 164 N, corresponding to a mass of 16.7 kg.
Highlight: When solving equilibrium problems, always equate the sum of clockwise moments to the sum of anticlockwise moments.
Forces in Action: Newton's Second Law
This page introduces Newton's second law of motion, which states that the net force acting on an object is equal to its mass multiplied by its acceleration .
Key points:
- One newton is defined as the force required to accelerate a 1 kg mass by 1 m/s².
- Various forces are discussed, including weight, upthrust, friction, and normal forces.
Definition: Newton's second law of motion states that F = ma, where F is the net force, m is mass, and a is acceleration.
Example: For a constant mass, if two forces of 2N upward and 1N downward are applied, the net force is 1N upward.
Vocabulary: Normal force is the force exerted by a surface on an object in contact with it, always perpendicular to the surface.
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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 S
iOS 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 Klich
Android 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.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
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 S
iOS 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 Klich
Android 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.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
Newton's 2nd Law of Motion and Fun Physics Experiments for Class 9 and 11
Emma Corden
@emmacorden_rpll
Newton's Second Law of Motion and Fluid Mechanics: A Comprehensive Guide
This guide covers key concepts in physics, including Newton's 2nd law of motion, forces, free body diagrams, motion in fluids, moments, and pressure. It provides detailed explanations, examples,... Show more
Free Body Diagrams and Force Analysis
This page covers free body diagrams and provides examples of force analysis in various scenarios.
Key concepts:
- Free body diagrams use dots to represent objects and arrows to show forces.
- A detailed example of a helicopter lifting a mass is provided, demonstrating force calculations in different situations.
Highlight: When drawing free body diagrams, always use arrows to scale and a dot to represent the object.
Example: In the helicopter example, when the load experiences acceleration, the tension in the cable increases from 981N to 1081N.
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Practical Investigation of Motion in Fluid
This page describes a practical investigation of motion in fluid and introduces forces on a slope.
Key points:
- The practical investigation involves dropping a ball bearing through a viscous fluid and measuring its motion.
- Forces on a slope are broken down into components parallel and perpendicular to the plane.
Vocabulary: Terminal velocity is the constant speed reached by an object falling through a fluid when the drag force equals the gravitational force.
Definition: The center of gravity is the point at which the entire weight of an object seems to act.
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Moments and Force Analysis
This page introduces the concept of moments and provides examples of force analysis using trigonometry.
Key points:
- A moment is the product of force and the perpendicular distance from the pivot to the line of action of the force.
- The unit of moment is Newton-meter (Nm).
Definition: A moment is the turning effect of a force, calculated as the product of the force and the perpendicular distance from the pivot to the line of action of the force.
Example: For a force of 6N applied 0.1m from a pivot, the moment is 0.5 Nm.
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Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
The Principle of Moments and Force Couples
This page explains the principle of moments and introduces force couples and torques.
Key concepts:
- An object is in equilibrium when there is no net force acting on it and the sum of clockwise moments equals the sum of anticlockwise moments.
- Force couples consist of two equal and opposite forces acting in the same plane.
Definition: The principle of moments states that for an object in equilibrium, the sum of clockwise moments equals the sum of anticlockwise moments.
Vocabulary: A force couple consists of two equal and opposite forces acting in the same plane, creating a pure rotational effect.
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Pressure in Fluids and Archimedes' Principle
This page covers pressure in fluids and introduces Archimedes' Principle.
Key points:
- Pressure in a fluid is calculated as P = F/A = mg/A = ρgh
- Archimedes' Principle states that the upthrust on a submerged object equals the weight of fluid displaced.
Definition: Archimedes' Principle states that the upthrust acting on a body submerged in a liquid is equal to the weight of the liquid that has been displaced.
Formula: Pressure in a fluid is given by P = ρgh, where ρ is density, g is gravitational acceleration, and h is depth.
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Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Moments Practice Questions
This page provides practice questions on moments and their solutions.
Key points:
- Detailed solutions for moment calculations are provided, including trigonometric analysis.
- The principle of moments is applied to solve equilibrium problems.
Example: For a force of 5N applied at a 30° angle to a 0.2m lever arm, the moment is calculated as 5 × 0.1 = 0.5 Nm.
Highlight: When solving moment problems, always identify the perpendicular distance from the pivot to the line of action of the force.
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Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Additional Moment Problems and Solutions
This page continues with more practice problems on moments and their detailed solutions.
Key points:
- A comprehensive problem involving a balanced beam is solved step-by-step.
- The principle of moments is restated and applied to find unknown weights and masses.
Example: In a balanced beam problem, the unknown weight is calculated to be 164 N, corresponding to a mass of 16.7 kg.
Highlight: When solving equilibrium problems, always equate the sum of clockwise moments to the sum of anticlockwise moments.
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Forces in Action: Newton's Second Law
This page introduces Newton's second law of motion, which states that the net force acting on an object is equal to its mass multiplied by its acceleration .
Key points:
- One newton is defined as the force required to accelerate a 1 kg mass by 1 m/s².
- Various forces are discussed, including weight, upthrust, friction, and normal forces.
Definition: Newton's second law of motion states that F = ma, where F is the net force, m is mass, and a is acceleration.
Example: For a constant mass, if two forces of 2N upward and 1N downward are applied, the net force is 1N upward.
Vocabulary: Normal force is the force exerted by a surface on an object in contact with it, always perpendicular to the surface.
We thought you’d never ask...
What is the Knowunity AI companion?
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.
Where can I download the Knowunity app?
You can download the app from Google Play Store and Apple App Store.
Is Knowunity really free of charge?
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
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Google 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 S
iOS 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 Klich
Android 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.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
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 S
iOS 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 Klich
Android 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.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user