What is elastic potential energy?
Quick answer
Elastic potential energy is the energy stored in an object when it’s stretched, squashed or bent, like a stretched rubber band, a compressed spring or a drawn bow. When the object is released, that stored energy turns into movement (kinetic energy), which is why a rubber band flies across the room.
How it works
When you stretch a rubber band, you do work on it: your muscles push its molecules out of their relaxed positions. The rubber “wants” to spring back, so the energy you put in is stored until you let go. This is a type of potential energy, meaning stored energy that depends on position or shape.
The formula
For springs (and roughly for rubber bands, within limits):
E = ½ k x²
| Symbol | Meaning |
|---|---|
| E | Elastic potential energy, in joules (J) |
| k | Spring constant: how stiff the spring is |
| x | How far it’s stretched or compressed from its resting length, in meters |
Because x is squared, stretching something twice as far stores four times the energy. This comes from Hooke’s law (F = kx), described by English scientist Robert Hooke in 1676.
Everyday examples
| Object | Where the energy goes |
|---|---|
| Stretched rubber band | Into flight when released |
| Drawn bow | Into the arrow |
| Trampoline | Into bouncing you upward |
| Car suspension springs | Absorbing bumps |
| Wind-up toy or old clock spring | Slowly into motion |
| Squeezed stress ball | Back into its shape |
The elastic limit
Stretch something too far and it passes its elastic limit: it won’t return to its original shape, or it snaps. That’s why old rubber bands lose their stretch and why springs can be “overstretched.”
Other forms of energy
Energy can’t be created or destroyed, only changed from one form to another. Others include kinetic (motion), gravitational potential (height), chemical (food, batteries) and thermal (heat).
For more physics basics, see Newton’s three laws of motion. Light energy is turned into electricity in solar panels.
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