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Updated Mar 16, 2026
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Understanding Forces and Elasticity in Physics
Zofia
@zofia_577
1 / 4
Forces and Elasticity Basics
You can't just use one force to change an object's shape - you need at least two forces working together. Think about bending a ruler: one hand pushes down whilst the other holds it steady.
Deformation simply means changing an object's shape or size by applying forces. This happens in two main ways: elastic deformation (like stretching a rubber band that snaps back) and inelastic deformation .
When objects get longer under force, that's called extension. When they get shorter or squashed, that's compression. Hooke's Law gives us a neat formula to work with springs: Force = Spring Constant × Extension.
Quick Tip: Remember F = k × e - Force equals spring constant times extension!
Hooke's Law in Action
Let's see Hooke's Law working with a real example. If you apply 3 N of force to a spring and it stretches by 0.15 m, you can find the spring constant by rearranging the formula.
Spring Constant = Force ÷ Extension = 3 ÷ 0.15 = 20 N/m. This tells you how stiff the spring is - the higher the number, the stiffer it gets.
But here's the catch: Hooke's Law only works up to the limit of proportionality. Beyond this point, doubling the force won't double the extension anymore. The spring starts behaving differently and might not return to its original shape.
Remember: A stiffer spring has a higher spring constant and needs more force to stretch the same distance!
Elastic Potential Energy
When you stretch a spring, you're actually storing energy in it - this is called elastic potential energy. It's like loading a catapult; the energy gets released when the spring returns to its normal length.
The formula is: Elastic Potential Energy = 0.5 × Spring Constant × (Extension)². Notice that extension is squared - this means small changes in stretching create big changes in stored energy.
Here's a worked example: A spring with a 3 N/m spring constant stretched by 50 cm (0.5 m). The stored energy = 0.5 × 3 × (0.5)² = 0.5 × 3 × 0.25 = 0.375 J.
Top Tip: Always convert centimetres to metres before calculating - it's a common exam mistake to forget this step!
Understanding the Energy Calculation
The previous calculation shows why the squared term matters so much. When the extension was 0.5 m, squaring it gave us 0.25 m². This dramatically affects the final energy value.
Elastic potential energy is measured in joules (J), just like other forms of energy. As long as you don't stretch beyond the limit of proportionality, all the work you put in gets stored as potential energy.
This stored energy explains why springs are so useful - from car suspension to trampolines, they absorb energy and release it back efficiently.
Key Point: The energy stored increases rapidly as you stretch further - double the extension means four times the energy!
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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
Understanding Forces and Elasticity in Physics
Zofia
@zofia_577
Ever wondered why a spring bounces back or why a rubber band snaps into place? Forces and elasticity explain how objects change shape when pushed, pulled, or squashed - and whether they return to normal afterwards.
Forces and Elasticity Basics
You can't just use one force to change an object's shape - you need at least two forces working together. Think about bending a ruler: one hand pushes down whilst the other holds it steady.
Deformation simply means changing an object's shape or size by applying forces. This happens in two main ways: elastic deformation (like stretching a rubber band that snaps back) and inelastic deformation .
When objects get longer under force, that's called extension. When they get shorter or squashed, that's compression. Hooke's Law gives us a neat formula to work with springs: Force = Spring Constant × Extension.
Quick Tip: Remember F = k × e - Force equals spring constant times extension!
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Hooke's Law in Action
Let's see Hooke's Law working with a real example. If you apply 3 N of force to a spring and it stretches by 0.15 m, you can find the spring constant by rearranging the formula.
Spring Constant = Force ÷ Extension = 3 ÷ 0.15 = 20 N/m. This tells you how stiff the spring is - the higher the number, the stiffer it gets.
But here's the catch: Hooke's Law only works up to the limit of proportionality. Beyond this point, doubling the force won't double the extension anymore. The spring starts behaving differently and might not return to its original shape.
Remember: A stiffer spring has a higher spring constant and needs more force to stretch the same distance!
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Elastic Potential Energy
When you stretch a spring, you're actually storing energy in it - this is called elastic potential energy. It's like loading a catapult; the energy gets released when the spring returns to its normal length.
The formula is: Elastic Potential Energy = 0.5 × Spring Constant × (Extension)². Notice that extension is squared - this means small changes in stretching create big changes in stored energy.
Here's a worked example: A spring with a 3 N/m spring constant stretched by 50 cm (0.5 m). The stored energy = 0.5 × 3 × (0.5)² = 0.5 × 3 × 0.25 = 0.375 J.
Top Tip: Always convert centimetres to metres before calculating - it's a common exam mistake to forget this step!
Sign up to see the contentIt's free!
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Improve your grades
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Understanding the Energy Calculation
The previous calculation shows why the squared term matters so much. When the extension was 0.5 m, squaring it gave us 0.25 m². This dramatically affects the final energy value.
Elastic potential energy is measured in joules (J), just like other forms of energy. As long as you don't stretch beyond the limit of proportionality, all the work you put in gets stored as potential energy.
This stored energy explains why springs are so useful - from car suspension to trampolines, they absorb energy and release it back efficiently.
Key Point: The energy stored increases rapidly as you stretch further - double the extension means four times the energy!
We thought you’d never ask...
What is the Knowunity AI companion?
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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 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