物理で一番身近で実用的な「力と圧力」について学ぼう！なぜ画びょうは簡単に刺さるのか、なぜ船は浮くのか、これらの疑問がすべて解決できるよ。テストでもよく出るから、しっかりマスターしよう。
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Updated Apr 11, 2026
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力と圧力の基本: 浮力と大気圧を学ぼう
1 / 6
力と圧力の基本概念
力って目に見えないけど、物を動かしたり形を変えたりする働きのことだよ。君が毎日感じている重力も立派な力の一つなんだ。
力を正確に表すには力の三要素が必要だ。力の大きさ（単位：N＝ニュートン）、力の向き、そして作用点（どこに働くか）の3つ。これを矢印で表すと、長さが大きさ、矢印の方向が向き、矢印の根元が作用点になるよ。
圧力は1m²の面積にどれくらいの力が垂直に働いているかを表す。単位はPa（パスカル）で、これは実はN/m²と同じ意味だ。
💡 覚えておこう！ 質量100gの物体には約1Nの重力が働くよ。これを覚えておけば計算が楽になる！
いろいろな力の種類
身の回りには色々な力が働いているんだ。重力はリンゴが落ちる原因、弾性力はバネが元に戻ろうとする力だよ。
摩擦力は物の動きを邪魔する力で、これがないと歩くことすらできない。垂直抗力は机が本を支える力のように、物体を支える働きをしているんだ。
どの力も力の三要素（大きさ・向き・作用点）で表現できる。矢印で描くときは、矢の根元が作用点、矢先が向き、矢の長さが大きさを表すよ。
💡 実生活で確認！ 今すぐペンを持ち上げてみて。君の手が弾性力、地球が重力を与えているよ！
圧力の計算方法
圧力の公式は超重要だ：圧力（Pa）= 力（N）÷ 面積（m²）。同じ力でも面積が小さいほど圧力は大きくなるんだ。
画びょうの針が尖っているのはこの原理を利用しているよ。面積を小さくすることで、小さな力でも大きな圧力を生み出せるからだ。逆にスキーが雪に沈まないのは、面積を大きくして圧力を小さくしているからなんだ。
計算するときは単位変換に要注意！面積は必ずm²で計算すること。1m² = 10,000cm²だから、cm²で与えられたら10,000で割ることを忘れずに。
💡 計算のコツ 面積の単位変換でよくミスするから、cm²→m²は「10,000で割る」と覚えよう！
水圧と浮力の仕組み
水圧は水の重さによって生まれる圧力で、深いところほど大きくなる。しかも上下左右あらゆる方向から働くんだ。ペットボトルに穴を開けると、下の穴から出る水が一番勢いよく飛ぶのはこの理由だよ。
浮力は水中の物体が上向きに受ける力のこと。実は物体の上面より下面の方に大きな水圧が働くから、その差で上向きの力が生まれるんだ。
アルキメデスの原理によると、浮力の大きさは「物体が押しのけた水の重さ」と等しい。物体の重力より浮力が大きければ浮き、小さければ沈むよ。
💡 なるほど！ 船が浮くのは中が空洞で、たくさんの水を押しのけて大きな浮力を得ているからなんだ！
大気圧と計算練習
大気圧は空気の重さによる圧力で、普段は感じないけど実はとても大きな力が働いている。吸盤が壁にくっつくのも、ストローでジュースが飲めるのも大気圧のおかげだよ。
計算問題では単位変換が超重要！質量（g）→力（N）は100で割る、面積（cm²）→（m²）は10,000で割ることを絶対覚えておこう。例えば1.2kgのレンガなら、1200g÷100=12Nの重力が働くんだ。
圧力の公式P=F/Sを使って、力12N、面積0.02m²なら、圧力は12÷0.02=600Paになる。手順を確実に覚えて、計算ミスを防ごう。
💡 テスト対策 単位変換の練習をたくさんやろう。ここでミスすると全部間違いになっちゃうよ！
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The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE Knowunity AI. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE Knowunity AI. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
力と圧力の基本: 浮力と大気圧を学ぼう
物理で一番身近で実用的な「力と圧力」について学ぼう！なぜ画びょうは簡単に刺さるのか、なぜ船は浮くのか、これらの疑問がすべて解決できるよ。テストでもよく出るから、しっかりマスターしよう。
力と圧力の基本概念
力って目に見えないけど、物を動かしたり形を変えたりする働きのことだよ。君が毎日感じている重力も立派な力の一つなんだ。
力を正確に表すには力の三要素が必要だ。力の大きさ（単位：N＝ニュートン）、力の向き、そして作用点（どこに働くか）の3つ。これを矢印で表すと、長さが大きさ、矢印の方向が向き、矢印の根元が作用点になるよ。
圧力は1m²の面積にどれくらいの力が垂直に働いているかを表す。単位はPa（パスカル）で、これは実はN/m²と同じ意味だ。
💡 覚えておこう！ 質量100gの物体には約1Nの重力が働くよ。これを覚えておけば計算が楽になる！
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いろいろな力の種類
身の回りには色々な力が働いているんだ。重力はリンゴが落ちる原因、弾性力はバネが元に戻ろうとする力だよ。
摩擦力は物の動きを邪魔する力で、これがないと歩くことすらできない。垂直抗力は机が本を支える力のように、物体を支える働きをしているんだ。
どの力も力の三要素（大きさ・向き・作用点）で表現できる。矢印で描くときは、矢の根元が作用点、矢先が向き、矢の長さが大きさを表すよ。
💡 実生活で確認！ 今すぐペンを持ち上げてみて。君の手が弾性力、地球が重力を与えているよ！
Sign up to see the contentIt's free!
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Improve your grades
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圧力の計算方法
圧力の公式は超重要だ：圧力（Pa）= 力（N）÷ 面積（m²）。同じ力でも面積が小さいほど圧力は大きくなるんだ。
画びょうの針が尖っているのはこの原理を利用しているよ。面積を小さくすることで、小さな力でも大きな圧力を生み出せるからだ。逆にスキーが雪に沈まないのは、面積を大きくして圧力を小さくしているからなんだ。
計算するときは単位変換に要注意！面積は必ずm²で計算すること。1m² = 10,000cm²だから、cm²で与えられたら10,000で割ることを忘れずに。
💡 計算のコツ 面積の単位変換でよくミスするから、cm²→m²は「10,000で割る」と覚えよう！
Sign up to see the contentIt's free!
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Improve your grades
Join milions of students
水圧と浮力の仕組み
水圧は水の重さによって生まれる圧力で、深いところほど大きくなる。しかも上下左右あらゆる方向から働くんだ。ペットボトルに穴を開けると、下の穴から出る水が一番勢いよく飛ぶのはこの理由だよ。
浮力は水中の物体が上向きに受ける力のこと。実は物体の上面より下面の方に大きな水圧が働くから、その差で上向きの力が生まれるんだ。
アルキメデスの原理によると、浮力の大きさは「物体が押しのけた水の重さ」と等しい。物体の重力より浮力が大きければ浮き、小さければ沈むよ。
💡 なるほど！ 船が浮くのは中が空洞で、たくさんの水を押しのけて大きな浮力を得ているからなんだ！
Sign up to see the contentIt's free!
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Improve your grades
Join milions of students
大気圧と計算練習
大気圧は空気の重さによる圧力で、普段は感じないけど実はとても大きな力が働いている。吸盤が壁にくっつくのも、ストローでジュースが飲めるのも大気圧のおかげだよ。
計算問題では単位変換が超重要！質量（g）→力（N）は100で割る、面積（cm²）→（m²）は10,000で割ることを絶対覚えておこう。例えば1.2kgのレンガなら、1200g÷100=12Nの重力が働くんだ。
圧力の公式P=F/Sを使って、力12N、面積0.02m²なら、圧力は12÷0.02=600Paになる。手順を確実に覚えて、計算ミスを防ごう。
💡 テスト対策 単位変換の練習をたくさんやろう。ここでミスすると全部間違いになっちゃうよ！
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
We thought you’d never ask...
What is the Knowunity AI companion?
Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
Where can I download the Knowunity app?
You can download the app from Google Play Store and Apple App Store.
Is Knowunity really free of charge?
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
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4.6/5
App Store
4.7/5
Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE Knowunity AI. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE Knowunity AI. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user