Potential Energy: Stored Energy

Core Idea

Potential energy is energy that is stored and waiting to be used. An object can have potential energy because of its position, its shape, or what it is made of. A ball held above the ground has potential energy because gravity can pull it down. A stretched rubber band has potential energy because it can snap back. This stored energy can be released and turned into motion or other forms of energy.

How It's Best Learned

Hold a ball at different heights and drop it to see how height affects the bounce. Stretch rubber bands to different lengths and launch small objects to see how stretch distance affects energy. Stack books at different heights and let them fall to observe the difference.

Common Misconceptions

• An object at rest has no energy. (It can have lots of potential energy due to its height, stretch, or chemical makeup.)
• Potential energy only comes from height. (Stretched springs, compressed air, batteries, and food all have potential energy.)
• Potential energy just sits there forever. (It can be released at any time and converted into kinetic energy or other forms.)
• Only heavy objects have significant potential energy. (Even a light object high up has meaningful potential energy — a small rock dropped from a tall building can do damage.)

Explainer

Imagine holding a ball above the ground. It is not moving, so it has no kinetic energy. But it definitely has energy — you can feel that it is ready to do something. The moment you let go, the ball falls, picks up speed, and slams into the ground. Where did that energy come from? It was there all along, stored as potential energy.

Gravitational potential energy is the most common type you encounter every day. Any object that is above the ground has it. The higher up the object is, the more gravitational potential energy it has because gravity has farther to pull it. A diver on a high diving board has more potential energy than one on a low board. When the diver jumps, that stored energy converts into kinetic energy as they speed toward the water.

But height is not the only way to store potential energy. A stretched rubber band has elastic potential energy — energy stored in the stretch. A compressed spring has it too. When you let go, the stored energy snaps the rubber band or pops the spring back to its original shape, converting into motion. The more you stretch or compress, the more energy is stored.

There is also chemical potential energy, which is stored in the bonds between atoms. Food has chemical potential energy that your body converts into movement and heat. A battery stores chemical potential energy that turns into electrical energy. Gasoline has chemical potential energy that a car engine converts into motion. Potential energy is everywhere, quietly waiting to be released. Understanding it helps explain why a roller coaster speeds up going downhill, why a bow launches an arrow, and why your body needs food to function.