Lift It with Just One Chopstick!? The Science Magic of Rice and a Plastic Bottle (Unleashing the Power of Friction!)
I’m Ken Kuwako, your Science Trainer. Every day is an experiment.
Would you believe me if I told you that you could lift a heavy plastic bottle packed solid with rice using just a single pair of chopsticks? You might think, “No way, that’s impossible!” But with just a “small trick,” you can make it rise up as if by magic. Today, I’m going to introduce this strange and fascinating science experiment. Everything you need is already in your home. Come on, let’s open the door to the magic of science together!
Let’s Try It! The Chopstick Challenge
First, let’s see just how surprising this phenomenon is by trying it the normal way.Step 1: The Regular WayPour the rice loosely into the plastic bottle, and gently slide the chopsticks into the center.
Now, hold the chopsticks and carefully try to lift the bottle. …What happened? Most likely, the chopsticks just slid right out. As expected, that’s the normal result.Step 2: The Magical TouchThis is where the real fun starts! Gently tap the rice-filled bottle on a desk or table. You’ll see the gaps between the rice grains start to close, and the overall volume will sink down a little. Keep adding more rice and tapping until the bottle is packed tightly with rice, leaving no space.Ready? Now, forcefully push the chopsticks into the very center of the tightly packed rice! Then, just like before, grab the chopsticks and try to lift the bottle…https://youtu.be/lm3PCtHfoQIncredibly, the entire heavy plastic bottle, packed solid with rice, lifts up together with the chopsticks! It’s as if the rice and chopsticks have been glued together with a powerful adhesive. Amazing, isn’t it?
The True Nature of the Magic: An Orchestra of Tiny Forces!
This phenomenon isn’t actually magic; the star of the show is a force that is very familiar to us: Friction.When you rub your hands together, they warm up—that’s thanks to friction. Friction is the force that acts on the surface where two objects touch, resisting motion between them.So why did the frictional force increase when we packed the rice so tightly? The key lies in another force called the Normal Force. While it sounds complicated, just think of it as “the force that pushes objects together.”By tapping the rice down, each grain is forced into a state where it is strongly pushing against its neighbors, the chopsticks, and the walls of the bottle, from all directions. The nature of this force is that the stronger this “pushing force (Normal Force)” becomes, the more the “force that resists movement (Friction)” increases proportionally. This relationship is expressed mathematically as:
f=μN
$\mu$ (mu) is the coefficient of friction (how slippery it is), and the most critical point here is N, the Normal Force. By packing the rice tightly, we made this N value extremely large.The friction generated by a single grain of rice is tiny, but there are thousands and tens of thousands of rice grains inside the bottle. When the tiny frictional forces created by these countless grains combine, they act like an orchestra to form one massive force, gripping the chopsticks firmly. The moment this combined force exceeds the total weight of the rice and the bottle, this surprising phenomenon occurs!This principle is an interesting property of what scientists call “granular material”—things made up of many powders or grains—and is an active area of research in science. Be sure to show off this science magic to your friends and family. They’ll be astonished!
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Make the wonders and fun of science more accessible! We provide easy-to-understand tips and fun science experiments you can do at home. Feel free to search around!・The content of our Science Notes has been published in a book. Find out more here・About the operator, Ken Kuwako: here・For various requests (writing, lectures, science classes, TV supervision, appearances, etc.): here・Article updates are distributed on X!
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