Maths
Chemistry
Biology
English Language
History
Responding to change (a2 only)
Infection and response
Homeostasis and response
Energy transfers (a2 only)
Cell biology
Organisms respond to changes in their internal and external environments (a-level only)
Biological molecules
Organisation
Substance exchange
Bioenergetics
Genetic information & variation
Inheritance, variation and evolution
Genetics & ecosystems (a2 only)
Ecology
Cells
Show all topics
Britain & the wider world: 1745 -1901
1l the quest for political stability: germany, 1871-1991
The cold war
Inter-war germany
Medieval period: 1066 -1509
2d religious conflict and the church in england, c1529-c1570
2o democracy and nazism: germany, 1918-1945
1f industrialisation and the people: britain, c1783-1885
1c the tudors: england, 1485-1603
2m wars and welfare: britain in transition, 1906-1957
World war two & the holocaust
2n revolution and dictatorship: russia, 1917-1953
2s the making of modern britain, 1951-2007
World war one
Britain: 1509 -1745
Show all topics
Physics
3 Dec 2025
35
5 pages
Ummi @ummi_.com
Ever wondered why you don't float away from Earth or how planets stay in orbit? The answer lies... Show more
Think of a gravitational field as an invisible bubble of influence around any object with mass. Just like how a magnet affects metal objects nearby, massive objects create these fields that pull on anything with mass within their reach.
Gravitational field strength (g) tells you how strong this pulling force is at any point. It's measured as the force per unit mass - basically, how much force a 1kg object would feel at that spot. This is a vector quantity, which means it has both size and direction (always pointing toward the massive object).
You'll also encounter gravitational potential (Φ), which represents the potential energy per unit mass at any point in the field. Think of it like being on a hill - the higher you are, the more potential energy you have.
Quick Tip Remember that 'g' on Earth's surface is approximately 9.8 N/kg - this is why objects accelerate downwards at 9.8 m/s² when dropped!
Newton figured out that every single object in the universe attracts every other object - yes, you're actually pulling on your desk right now! The strength of this attraction depends on two key factors.
First, the force increases with mass - the more massive the objects, the stronger they pull on each other. Second, distance matters hugely double the distance and the force becomes four times weaker (it follows an inverse square relationship).
The mathematical formula is F = G × (m₁ × m₂) / r², where G is the gravitational constant . This might look intimidating, but it simply tells you how to calculate the gravitational force between any two objects.
Real-world connection This same law explains why the International Space Station orbits Earth and why Mars takes longer to orbit the Sun than Earth does!
Here's where things get practical for your exams. Gravitational field strength (g) can be calculated using the formula g = GM/r², where M is the mass creating the field and r is your distance from its centre.
This formula shows why gravity feels weaker on the Moon (smaller mass) and why astronauts feel weightless in space stations (they're much further from Earth's centre). The further you go from a massive object, the weaker its gravitational field becomes.
Understanding this concept helps explain why satellites need different orbital speeds depending on their altitude, and why space missions require careful calculations to reach other planets.
Exam tip Always remember that 'r' is measured from the centre of the object, not its surface - this catches many students out in exam questions!
Gravitational potential (Φ) uses the formula Φ = -GM/r. The negative sign isn't just mathematical decoration - it tells us that potential energy decreases as objects get closer to the source. Think of rolling a ball downhill; it naturally moves toward lower potential energy.
Gravitational field lines are imaginary arrows that show the direction of gravitational force at every point in space. These lines always point toward the mass creating the field, and their density indicates field strength - closer lines mean stronger fields.
These concepts help visualise how gravitational fields work in three-dimensional space, making it easier to understand complex orbital mechanics and satellite motion.
Visual learning Try sketching field lines around Earth - they point inward from all directions, getting denser closer to the surface!
Gravitational fields aren't just theoretical - they govern some of the most spectacular phenomena in our universe. Orbital motion keeps the Moon circling Earth and maintains the International Space Station's path around our planet.
The tides you see at the beach result from the Moon's and Sun's gravitational fields tugging on Earth's oceans. Even more extreme, black holes have gravitational fields so intense that not even light can escape once it gets too close.
In cosmology, gravitational fields shape the entire universe's structure, pulling matter together to form galaxies and governing how the universe evolves over billions of years.
Mind-blowing fact GPS satellites must account for gravitational field differences to maintain accuracy - without this, your sat-nav would be off by several kilometres!
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.
0
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
App Store
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
Ummi
@ummi_.com
Ever wondered why you don't float away from Earth or how planets stay in orbit? The answer lies in gravitational fields - invisible forces that surround every object with mass. Understanding gravitational fields is crucial for GCSE and A-level physics,... Show more
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Think of a gravitational field as an invisible bubble of influence around any object with mass. Just like how a magnet affects metal objects nearby, massive objects create these fields that pull on anything with mass within their reach.
Gravitational field strength (g) tells you how strong this pulling force is at any point. It's measured as the force per unit mass - basically, how much force a 1kg object would feel at that spot. This is a vector quantity, which means it has both size and direction (always pointing toward the massive object).
You'll also encounter gravitational potential (Φ), which represents the potential energy per unit mass at any point in the field. Think of it like being on a hill - the higher you are, the more potential energy you have.
Quick Tip: Remember that 'g' on Earth's surface is approximately 9.8 N/kg - this is why objects accelerate downwards at 9.8 m/s² when dropped!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Newton figured out that every single object in the universe attracts every other object - yes, you're actually pulling on your desk right now! The strength of this attraction depends on two key factors.
First, the force increases with mass - the more massive the objects, the stronger they pull on each other. Second, distance matters hugely: double the distance and the force becomes four times weaker (it follows an inverse square relationship).
The mathematical formula is F = G × (m₁ × m₂) / r², where G is the gravitational constant . This might look intimidating, but it simply tells you how to calculate the gravitational force between any two objects.
Real-world connection: This same law explains why the International Space Station orbits Earth and why Mars takes longer to orbit the Sun than Earth does!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Here's where things get practical for your exams. Gravitational field strength (g) can be calculated using the formula g = GM/r², where M is the mass creating the field and r is your distance from its centre.
This formula shows why gravity feels weaker on the Moon (smaller mass) and why astronauts feel weightless in space stations (they're much further from Earth's centre). The further you go from a massive object, the weaker its gravitational field becomes.
Understanding this concept helps explain why satellites need different orbital speeds depending on their altitude, and why space missions require careful calculations to reach other planets.
Exam tip: Always remember that 'r' is measured from the centre of the object, not its surface - this catches many students out in exam questions!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Gravitational potential (Φ) uses the formula Φ = -GM/r. The negative sign isn't just mathematical decoration - it tells us that potential energy decreases as objects get closer to the source. Think of rolling a ball downhill; it naturally moves toward lower potential energy.
Gravitational field lines are imaginary arrows that show the direction of gravitational force at every point in space. These lines always point toward the mass creating the field, and their density indicates field strength - closer lines mean stronger fields.
These concepts help visualise how gravitational fields work in three-dimensional space, making it easier to understand complex orbital mechanics and satellite motion.
Visual learning: Try sketching field lines around Earth - they point inward from all directions, getting denser closer to the surface!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Gravitational fields aren't just theoretical - they govern some of the most spectacular phenomena in our universe. Orbital motion keeps the Moon circling Earth and maintains the International Space Station's path around our planet.
The tides you see at the beach result from the Moon's and Sun's gravitational fields tugging on Earth's oceans. Even more extreme, black holes have gravitational fields so intense that not even light can escape once it gets too close.
In cosmology, gravitational fields shape the entire universe's structure, pulling matter together to form galaxies and governing how the universe evolves over billions of years.
Mind-blowing fact: GPS satellites must account for gravitational field differences to maintain accuracy - without this, your sat-nav would be off by several kilometres!
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.
0
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
App Store
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
Sociology