Slinky Science

Have you ever played with a Slinky? Maybe you launched it from the top of the steps and watched it march down. Or you might have stretched it way, way out and let it spring back together. As you played with that Slinky, did you notice it had two kinds of energy? It’s true! A Slinky can be more than just fun. It can teach you science.

Two Kinds of Energy

James Valles is a physicist at Brown University. That means he studies energy. He says you can learn about different kinds of energy with a Slinky. One kind is called potential energy. That means stored energy. Another kind is kinetic energy. That’s the energy of motion. “You store energy, and then you release it, and it’ll give you motion,” Valles explains. Think of it like stretching a rubber band to make it fly across the room. Pulling the rubber band back loads it with potential energy, and when you let it go to sail through the air, that’s kinetic energy.

The way a Slinky works is similar. “When a Slinky is walking down stairs,” Valles points out, “you see potential energy turned into kinetic energy.” A Slinky at the top of the steps has potential energy. “Potential energy is giving something the power to move on its own later,” Valles says. So, the Slinky at the top of the stairs can’t move yet. It doesn’t start to go on its own until you pull one end down to the first step. Then gravity takes over. Gravity is the force that pulls everything toward Earth’s surface. It’s what keeps your feet on the ground. Gravity also pulls on the Slinky as it moves down the steps.

How A Slinky Walks

Gravity’s pull gets the Slinky moving when you let the toy go. This movement is kinetic energy. The Slinky’s coils stretch as it moves. They pull as they stretch, loading up with stored energy again. When the coils bunch up, the Slinky flips over. “If you look very closely,” Valles says, “you’ll see the coils get closer together as it starts to snap over. That’s the spring pulling on itself. It has the stored energy that allows it to pull on itself to fling it over. It’s stored energy turning into motion energy.”

Stretching and bunching up moves the Slinky, but it also needs gravity’s pull to keep going. That’s why it stops when it reaches the bottom of the steps. That’s also why it works on stairs but not a flat floor. What do you think might happen if you put a Slinky on a ramp? Would it still walk down?

More Slinky Science

You can use a Slinky to understand potential and kinetic energy even if you don’t have stairs. Hold a Slinky up in the air by one end. Wait until it stops moving. Then pull the bottom of the Slinky down and let go. Did you see the Slinky go up? Valles explains what happened: “When you pull it down, you give it stored energy, then it turns into motion when you let it go.” A moving Slinky is potential energy turning into kinetic energy over and over again.

Now hold one end of a Slinky in each hand on top of a table or the floor. Spread your hands apart and stretch it as far as you can. What kind of energy does the Slinky have while it’s stretched out? If you said potential energy, you’re right! Now let the Slinky go. What kind of energy did you see as the Slinky snapped back together? If you said kinetic energy, right again!

Sometimes you can learn a lot from a simple toy!