Ever wondered why a spring bounces back or why a...
Physics546 views·Updated 21 Aug 2026·4 pagesUnderstanding Forces and Elasticity in Physics
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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 (like squashing Play-Doh that stays squashed).
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!
2
of 4
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!
3
of 4
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!
4
of 4
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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Physics546 views·Updated 21 Aug 2026·4 pagesUnderstanding 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.
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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 (like squashing Play-Doh that stays squashed).
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!
2
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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!
3
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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!
4
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- Improve your grades
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By signing up you accept Terms of Service and Privacy Policy
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...
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.
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