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Updated Mar 20, 2026
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Comprehensive Physics Revision Guide
Isha Patel
@ishx_0119
1 / 5
States of Matter and Density
Ever wondered why you can't squash a rock but you can compress air in a bike pump? It's all about how particles are arranged and behave in solids, liquids, and gases.
In solids, particles are tightly packed and only vibrate in fixed positions - that's why your desk doesn't randomly change shape! Liquids have weaker forces between particles, so they can flow and take the shape of containers whilst staying the same volume. Gases have particles that move freely with loads of space between them, which is why you can compress air.
Density is simply how much mass is crammed into a space - think of it as how "heavy" something feels for its size. The formula is: Density = mass ÷ volume. When measuring irregular objects, you can use water displacement methods like an eureka can to find the volume.
Quick Tip: Remember that denser liquids sink below less dense ones - that's why oil floats on water!
Heat Transfer and Energy
Heat always moves from hot to cold objects - never the other way around. There are three ways this happens: conduction (through solids), convection (in liquids and gases), and radiation (through empty space, like heat from the Sun).
Conduction works because heated particles vibrate more vigorously and bump into their neighbours, passing energy along. This is why metal spoons get hot when you leave them in hot soup.
Specific heat capacity tells you how much energy is needed to heat up 1kg of a material by 1°C. You can measure this using a heater, thermometer, and some careful timing. Internal energy is the total kinetic and potential energy of all particles in a system.
When substances change state (like ice melting), they need specific latent heat - energy that breaks bonds without changing temperature. The formula is E = mL, where L is the specific latent heat.
Remember: During state changes, temperature stays constant even though you're adding energy!
Forces, Moments and Pressure
Your centre of mass is where all your weight seems to be concentrated - it's why you spread your legs wider on a wobbly bus to stay balanced! You can find it for irregular shapes by hanging them from different points and seeing where the lines cross.
Stability depends on two things: having a wide base and keeping your centre of mass low. Think about why sports cars are low and wide whilst double-decker buses have heavy engines at the bottom.
Moments create turning effects around a pivot point. The formula is Moment = Force × distance from pivot. For balance, clockwise moments must equal anticlockwise moments - that's why spanners have long handles for extra turning power.
In fluids (liquids and gases), pressure increases with depth because the weight of fluid above pushes down. The formula is Pressure = density × height × gravity. This explains why your ears pop when diving deep or going up mountains.
Real-world connection: Hydraulic car jacks use fluid pressure to lift heavy cars with relatively little force!
Upthrust and Atmospheric Pressure
Upthrust explains why some things float whilst others sink - it's the upward force that fluids exert on objects. If an object's weight equals the upthrust, it floats. If the weight is greater than upthrust, it sinks.
Here's the key rule: denser objects sink, less dense objects float. A steel ship floats because its overall density (including all the air inside) is less than water, even though steel itself is denser than water.
Atmospheric pressure decreases as you go higher up mountains because there are fewer air molecules above you pressing down. Gravity pulls most air molecules closer to Earth's surface, leaving less air at higher altitudes.
This pressure difference is why your crisp packets puff up on aeroplanes and why mountain climbers need oxygen masks at extreme heights.
Fun fact: The pressure at the bottom of the ocean is over 1000 times greater than at sea level - enough to crush a submarine!
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Students love us — and so will you.
4.6/5
App Store
4.7/5
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 Knowunity AI. 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 Knowunity AI. 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
Comprehensive Physics Revision Guide
Isha Patel
@ishx_0119
Physics can seem overwhelming, but it's actually all around you - from why ice floats in your drink to how pressure cookers work. This revision guide breaks down the essential physics concepts you need to master, covering everything from the... Show more
States of Matter and Density
Ever wondered why you can't squash a rock but you can compress air in a bike pump? It's all about how particles are arranged and behave in solids, liquids, and gases.
In solids, particles are tightly packed and only vibrate in fixed positions - that's why your desk doesn't randomly change shape! Liquids have weaker forces between particles, so they can flow and take the shape of containers whilst staying the same volume. Gases have particles that move freely with loads of space between them, which is why you can compress air.
Density is simply how much mass is crammed into a space - think of it as how "heavy" something feels for its size. The formula is: Density = mass ÷ volume. When measuring irregular objects, you can use water displacement methods like an eureka can to find the volume.
Quick Tip: Remember that denser liquids sink below less dense ones - that's why oil floats on water!
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
Heat Transfer and Energy
Heat always moves from hot to cold objects - never the other way around. There are three ways this happens: conduction (through solids), convection (in liquids and gases), and radiation (through empty space, like heat from the Sun).
Conduction works because heated particles vibrate more vigorously and bump into their neighbours, passing energy along. This is why metal spoons get hot when you leave them in hot soup.
Specific heat capacity tells you how much energy is needed to heat up 1kg of a material by 1°C. You can measure this using a heater, thermometer, and some careful timing. Internal energy is the total kinetic and potential energy of all particles in a system.
When substances change state (like ice melting), they need specific latent heat - energy that breaks bonds without changing temperature. The formula is E = mL, where L is the specific latent heat.
Remember: During state changes, temperature stays constant even though you're adding energy!
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
Forces, Moments and Pressure
Your centre of mass is where all your weight seems to be concentrated - it's why you spread your legs wider on a wobbly bus to stay balanced! You can find it for irregular shapes by hanging them from different points and seeing where the lines cross.
Stability depends on two things: having a wide base and keeping your centre of mass low. Think about why sports cars are low and wide whilst double-decker buses have heavy engines at the bottom.
Moments create turning effects around a pivot point. The formula is Moment = Force × distance from pivot. For balance, clockwise moments must equal anticlockwise moments - that's why spanners have long handles for extra turning power.
In fluids (liquids and gases), pressure increases with depth because the weight of fluid above pushes down. The formula is Pressure = density × height × gravity. This explains why your ears pop when diving deep or going up mountains.
Real-world connection: Hydraulic car jacks use fluid pressure to lift heavy cars with relatively little force!
Sign up to see the contentIt's free!
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Improve your grades
Join milions of students
Upthrust and Atmospheric Pressure
Upthrust explains why some things float whilst others sink - it's the upward force that fluids exert on objects. If an object's weight equals the upthrust, it floats. If the weight is greater than upthrust, it sinks.
Here's the key rule: denser objects sink, less dense objects float. A steel ship floats because its overall density (including all the air inside) is less than water, even though steel itself is denser than water.
Atmospheric pressure decreases as you go higher up mountains because there are fewer air molecules above you pressing down. Gravity pulls most air molecules closer to Earth's surface, leaving less air at higher altitudes.
This pressure difference is why your crisp packets puff up on aeroplanes and why mountain climbers need oxygen masks at extreme heights.
Fun fact: The pressure at the bottom of the ocean is over 1000 times greater than at sea level - enough to crush a submarine!
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
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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Most popular content in Physics
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Can't find what you're looking for? Explore other subjects.
Students love us — and so will you.
4.6/5
App Store
4.7/5
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 Knowunity AI. 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 Knowunity AI. 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