【Quiz】Which Is Heavier After the Cut? A Carrot at the Balance Point! – Exploring Torque with Vegetables
I’m Ken Kuwako, your Science Trainer. Every day is an experiment!
Sometimes, our intuition gets “tricked” by the laws of physics. For instance, imagine a single carrot perfectly balanced on a string. If you were to cut that carrot right at the balancing point, wouldn’t you think both sides would weigh the same? Surprisingly, this simple scenario hides a secret of physics that supports our daily lives. Today, I’ve got a “Physics Quiz” that might make your brain itch a little. Let’s think through it together!
Quick Quiz Time! Ta-da!
Suppose we hang a carrot by a string like this. (Try to visualize the diagram!)
In this setup, we tied the string slightly to the right of the center, on the thicker side, to keep it perfectly horizontal. Now, here is the challenge: If we were to slice the carrot in two exactly where the string is, which part would be heavier: the left side (the thin end) or the right side (the thick end)?
Take a moment to think about it. Got an answer? Let’s reveal the truth! I’ll explain the answer in this video.
A Surprising Result! The weights were actually different?
Believe it or not, they aren’t equal! One side is clearly heavier. “Wait, which one?” you might ask. This is a classic masterpiece in the world of physics puzzles. Let’s break down why the weights differ. The keyword here is Moment of Force (or Torque).
For the thick side:
68g
And for the thin side: 
56g
That’s right—the thick side is heavier!
The thick side is heavier, while the thin side is lighter.
Why does this happen? Let’s use a bit of mathematical logic to solve this mystery.
What is the “Turning Force”? Understanding Moments
Imagine trying to loosen a rusty bolt with a wrench. If you want to apply the strongest force possible, where do you grab the wrench? Instinctively, you probably grab the very end of the handle. This is because the further you are from the center (the axis of rotation), the more “turning power” you generate with less effort. This concept is called a Moment. Mathematically, it looks like this:
M = F × L
Moment = Force × Arm Length
This formula is vital! It’s not just about the “weight (force)”; the “distance from the center (arm length)” is what ultimately determines the rotational strength.
When Moments Balance Out
Let’s make a simple mobile using a light rod and two identical weights. In this case, if you tie the string exactly in the middle of the rod, it stays perfectly level.
If we calculate the moments around the string (the axis), they are equal on both sides:
Left side: 2N × 10cm = 20N·cm (Counter-clockwise)
Right side: 2N × 10cm = 20N·cm (Clockwise)
When the clockwise and counter-clockwise moments are equal, the object stops rotating and stays still. We call this “Moment Equilibrium.”
What happens when we hang different weights?
Now, let’s get to the heart of the matter. Let’s hang two different weights: a heavy 6N ball and a light 2N ball. To make them balance, you can’t tie the string in the middle; you have to shift it closer to the heavier side.
In practice, they will balance at a point like this:
Left side: 6N × 5cm = 30N·cm
Right side: 2N × 15cm = 30N·cm
The math checks out—the moments are identical! But if we were to snip the rod right at the string…
Naturally, the left piece (carrying the 6N weight) is much heavier than the right piece (carrying the 2N weight).
The Carrot Mystery Solved!
Now, let’s go back to our original carrot.
The string was tied much closer to the thick end than the thin end. This is exactly the same situation as our “6N vs 2N” experiment.
Because the thin, long part is far from the center (the string), even a small weight can generate a large moment (turning force). Conversely, because the thick part is so close to the center, it has to be significantly heavier to maintain the balance. Therefore, the answer is: The thick half is heavier! When you visualize the forces, it looks something like this:
When you look through the lens of physics, even a single vegetable in the supermarket becomes a gateway to a world of beautiful equations and balance. I’ve shared many more fascinating problems like this in my textbook for the Science Proficiency Test. Check it out if you’re curious!
Inquiries & Requests
Bringing the wonder and fun of science closer to you! I’ve compiled plenty of fun experiments you can do at home and the tips to make them work. Feel free to explore!
My “Science Notebook” content is now a book! Details here.
Learn more about the author, Ken Kuwako, here.
For requests (writing, speaking, science workshops, TV supervision/appearances, etc.), click here. – Get the latest updates on X (formerly Twitter)!
Watch experiment videos on the Science Material Channel!
２月のイチオシ実験！梱包材で遊ぼう！
- 静電気の時期になってきました。子供と一緒に梱包材で盛り上がろう！→ やめられなくなる！静電気実験２０
体中に梱包材をはりつけてみよう！
テレビ番組等・科学監修等のお知らせ
- 「月曜から夜更かし」（日本テレビ）にて科学監修・出演しました。
書籍のお知らせ
- 1/27 『見えない力と遊ぼう！電気・磁石・熱の実験』（工学社）を執筆しました。
- サクセス15 ２月号にて「浸透圧」に関する科学記事を執筆しました。
- 『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）
- 『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。
講師等・ショー・その他お知らせ
- 2/20（金）「生徒の進学希望実現支援事業」研究授業＠福井県立若狭高等学校 講師
- 3/20（金） 日本理科教育学会オンライン全国大会2026「慣性の法則の概念形成を目指した探究的な学びの実践」について発表します。B会場 第３セッション： 学習指導・教材（中学校）③ 11:20-12:20
- 7/18（土） 教員向け実験講習会「ナリカカサイエンスアカデミー」の講師をします。お会いしましょう。
- 10/10（土） サイエンスショー予定
- 各種SNS X(Twitter)／instagram／Facebook／BlueSky／Threads
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。
