Elastic Potential Energy
A stretched spring stores energy: ½kx².
About this topic
A stretched or compressed spring stores elastic potential energy: EPE = ½kx², equal to the area under a force-extension graph. Doubling the stretch stores four times as much energy.
The energy is released when the spring returns to shape, launching a dart, powering a toy or bouncing a trampoline user. The formula comes from the average force ½kx times distance x. It applies up to the elastic limit, and energy conservation can link it to kinetic energy: ½kx² = ½mv² for a released mass on a smooth surface.
Example: a spring with k = 200 N/m compressed by 0.1 m stores 0.5 x 200 x 0.01 = 1 J. If this launches a 0.05 kg ball, it leaves at about 6.3 m/s. Bows, pogo sticks, clock springs, vaulting poles and car suspensions store and release energy in this way. Rubber bands and bouncing balls also store elastic energy.
Common errors: using x as the total length instead of the extension, forgetting the half, and forgetting that the stored energy is not equal to force times distance, since force changes as the spring stretches.
Key ideas
- Energy grows with the square of stretch
- Released as motion
- Works for bows and trampolines
Quick check
Use cases: where Elastic Potential Energy helps
- Homework: review the key idea behind Elastic Potential Energy before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Elastic Potential Energy without notes.
- Visual learning: play with the interactive lab to see how Elastic Potential Energy changes when you adjust its inputs.
- Teaching a friend: explain Elastic Potential Energy in your own words, then compare your version with the key ideas.
The same laws describe car crashes, sports, satellites and everyday machines.
Frequently asked questions
What is Elastic Potential Energy?
A stretched spring stores energy: ½kx².
What will I learn in Elastic Potential Energy?
Energy grows with the square of stretch. Released as motion. Works for bows and trampolines.
Is Elastic Potential Energy part of Physics?
Yes. It is one of 150 Physics topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Elastic Potential Energy lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Elastic Potential Energy?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.