2026年4月6日 / Last updated : 2026年4月6日 桑子 研 Science

A Split-Second Miracle! Capture the “Law of Inertia” Hidden Inside a Water Balloon!

Hi, I’m Ken Kuwako, your Science Trainer. Every day is an experiment!

Have you ever taken a really close look at the exact moment a water balloon pops? To our eyes, it’s a blink-and-you-miss-it event, but that tiny fraction of a second is packed with the beauty and mystery of physics. Today, I’ll show you how I used a smartphone app to visualize this “split-second magic” that is usually invisible to the naked eye.

Freezing Time with Technology

I filled a balloon with plenty of water and used a burst-shot app to capture the moment it burst and the water was set free. I used to use an app called “300 Fast Shots”—which, as the name suggests, took photos at incredible speeds—but unfortunately, it is no longer being distributed.

But there is no need to worry! Modern smartphone cameras have far surpassed the specialized apps of the past. By using the standard slow-motion feature on your phone, anyone can easily witness these same mystical scenes for themselves.

Drama in 1/30th of a Second

I actually performed this water balloon experiment on stage, and seeing it live is a truly special experience. When the slow-motion footage played on the big screen, a collective “Whoa!” rippled through the audience.

These photos were taken at a rate of one frame every 1/30th of a second. While watching a smooth video is great, there’s something fascinating about “turning the pages” of time, one still frame at a time, to see what you can find.

The Mystery of Why Water “Stays Put”

Here is what happened with a different balloon. You can see the water splashes a bit differently this time. Small factors like the thickness of the rubber or exactly where it tore give each splash its own unique “personality.”

Take a close look at the shape of the water right after the pop. Even though the rubber is completely gone, for a fleeting moment, the water remains suspended in mid-air, perfectly maintaining the shape of the balloon. It looks like a “ghost” of the water, doesn’t it?

This is a phenomenon caused by Inertia, which we learn about in science class. Because “objects at rest tend to stay at rest,” the water doesn’t move immediately when the outer rubber snaps away—it tries to stay exactly where it was.

Go Find the “Hidden Science” in Your Daily Life

Finally, I found a video compiling this sequence of movements. Take a look!

Within the “instants” we usually overlook, the laws of nature are being perfectly illustrated. You don’t need fancy equipment—with just the smartphone in your hand, the world can become a much more interesting place. Why not grab your camera, capture a “moment” nearby, and see what scientific discoveries you can find?

Inquiries and Requests

Bringing the mystery and fun of science closer to you! I’ve put together fun experiments you can do at home and easy-to-understand tips. Feel free to explore!
・The “Science Resource Collection” is now a book! Details here.
・About the creator, Ken Kuwako: here.
・For various requests (writing, speaking, workshops, TV supervision, etc.): here.
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Check out experiment videos on the Science Resource Channel!

４月のイチオシ実験！

テレビ番組・科学監修等のお知らせ

  • 4月9日（木）「THE突破ファイル」（日本テレビ ）の科学監修を行いました。夜7時〜となります。

書籍のお知らせ

  • サクセス15 ４月号にて、野球の科学について記事を執筆しました（2026/3）
  • 『大人のための高校物理復習帳』（講談社）…一般向けに日常の物理について公式を元に紐解きました。特設サイトでは実験を多数紹介しています。※増刷がかかり６刷となりました（2026/02/01） スクリーンショット 2014-07-05 0.43.51
  • 『きめる!共通テスト 物理基礎 改訂版』（学研）…　高校物理の参考書です。イラストを多くしてイメージが持てるように描きました。授業についていけない、物理が苦手、そんな生徒におすすめです。特設サイトはこちら。

講師・ショー・研究等のお知らせ

Explore

  • 楽しい実験…お子さんと一緒に夢中になれるイチオシの科学実験を多数紹介しています。また、高校物理の理解を深めるための動画教材も用意しました。
  • 理科の教材… 理科教師をバックアップ！授業の質を高め、準備を効率化するための選りすぐりの教材を紹介しています。
  • Youtube…科学実験等の動画を配信しています。
  • 科学ラジオ …科学トピックをほぼ毎日配信中！AI技術を駆使して作成した「耳で楽しむ科学」をお届けします。
  • 講演 …全国各地で実験講習会・サイエンスショー等を行っています。
  • About …「科学のネタ帳」のコンセプトや、運営者である桑子研のプロフィール・想いをまとめています。
  • お問い合わせ …実験教室のご依頼、執筆・講演の相談、科学監修等はこちらのフォームからお寄せください。
 
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