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Physics
Understanding Newton's Laws of Motion
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Nov 21, 2025
•
Newton's Laws of Motion Explained
U
ur mom sksk
@urmomsksk_sadx
1 / 5
Newton's Laws of Motion
Isaac Newton established three powerful laws that explain how objects behave when forces act on them. These laws are the building blocks of physics that you'll use throughout your science classes.
The First Law (Law of Inertia) states that an object at rest stays at rest, and an object in motion stays in motion unless a force acts on it. This explains why you jerk forward when a car suddenly stops—your body wants to keep moving!
The Second Law shows that force equals mass times acceleration . This relationship is directly proportional with force and acceleration but inversely proportional with mass .
Quick Tip: Think of Newton's Second Law next time you're pushing a shopping cart. Notice how it's easier to push an empty cart (less mass) than a full one, even when you apply the same force!
The Third Law tells us that for every action, there's an equal and opposite reaction. When you jump, you push down on the ground, and the ground pushes back up on you with equal force.
Types of Forces
Forces come in various forms that affect objects differently. Understanding these helps you analyze real-world situations using Newton's laws.
The force of gravity (Fg) pulls objects toward Earth's center and is also known as weight. This universal force keeps your feet on the ground and makes objects fall when dropped.
Normal force (FN) is a contact force that acts perpendicular (at 90°) to the point where objects touch. When you sit on a chair, the chair pushes up on you with normal force to balance gravity.
Friction is the force that opposes motion between surfaces. It's why you can walk without slipping and why your bike eventually stops when you stop pedaling.
Remember: Tension is the force transmitted through cables, strings, or ropes. Next time you see a hanging light or a tow truck pulling a car, you're witnessing tension forces in action!
Calculating with F=ma
Newton's Second Law gives us a powerful equation to solve real-world problems involving forces, mass, and acceleration.
To find acceleration when you know force and mass, divide force by mass . In Example 1, with a force of 25N applied to a 10kg object, the acceleration equals 2.5 m/s².
When finding mass with known force and acceleration, rearrange the equation to m = F/a. In Example 2, an object experiencing 4,500N of force with 3.0 m/s² acceleration has a mass of 1,500kg.
Problem-Solving Tip: Always check your units! Acceleration should be in m/s², mass in kg, and force in Newtons. Keeping your units consistent prevents calculation errors.
Free-Body Diagrams
Free-body diagrams are visual tools that show all forces acting on an object, making Newton's laws easier to apply to real situations.
When creating these diagrams, remember that force arrows have both size and direction. Vertical forces typically point up or down, while horizontal forces point left or right. Always label each force clearly (Fg for gravity, FN for normal force, etc.).
A simple example is a book resting on a table. The diagram would show two forces: gravity pulling down and the normal force pushing up. Since the book isn't moving, these forces must be equal.
Drawing Tip: When creating free-body diagrams, start by drawing the object as a simple dot or box, then add force arrows pointing away from the object. Make arrow lengths proportional to force strengths!
Key Physics Vocabulary
Understanding the vocabulary of motion helps you communicate scientific ideas precisely and solve physics problems correctly.
Force is simply a push or pull measured in Newtons (N). Think of force whenever you push a door open, lift a backpack, or kick a soccer ball.
Acceleration means change in velocity over time, measured in meters per second squared . It's not just speeding up—slowing down is negative acceleration! A car going from 0 to 65 mph demonstrates acceleration.
Mass represents the amount of matter in an object, measured in kilograms (kg). It's different from weight—your mass stays the same whether you're on Earth or the moon.
Concept Check: Inertia is an object's resistance to changes in motion. Next time you slam on the brakes and feel yourself lurch forward, you're experiencing inertia in action!
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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
I think it’s very much worth it and you’ll end up using it a lot once you get the hang of it and even after looking at others notes you can still ask your Artificial intelligence buddy the question and ask to simplify it if you still don’t get it!!! In the end I think it’s worth it 😊👍 ⚠️Also DID I MENTION ITS FREEE YOU DON’T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLY❗️❗️⚠️
Thomas R
iOS user
Knowunity is the BEST app I’ve used in a minute. This is not an ai review or anything this is genuinely coming from a 7th grade student (I know 2011 im young) but dude this app is a 10/10 i have maintained a 3.8 gpa and have plenty of time for gaming. I love it and my mom is just happy I got good grades
Brad T
Android user
Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help🤍🤍
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
I found this app a couple years ago and it has only gotten better since then. I really love it because it can help with written questions and photo questions. Also, it can find study guides that other people have made as well as flashcard sets and practice tests. The free version is also amazing for students who might not be able to afford it. Would 100% recommend
Aubrey
iOS user
Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.😋🩷🎀
Marco B
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. 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 app is phenomenal down to the correct info and the various topics you can study! I greatly recommend it for people who struggle with procrastination and those who need homework help. It has been perfectly accurate for world 1 history as far as I’ve seen! Geometry too!
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
I think it’s very much worth it and you’ll end up using it a lot once you get the hang of it and even after looking at others notes you can still ask your Artificial intelligence buddy the question and ask to simplify it if you still don’t get it!!! In the end I think it’s worth it 😊👍 ⚠️Also DID I MENTION ITS FREEE YOU DON’T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLY❗️❗️⚠️
Thomas R
iOS user
Knowunity is the BEST app I’ve used in a minute. This is not an ai review or anything this is genuinely coming from a 7th grade student (I know 2011 im young) but dude this app is a 10/10 i have maintained a 3.8 gpa and have plenty of time for gaming. I love it and my mom is just happy I got good grades
Brad T
Android user
Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help🤍🤍
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
I found this app a couple years ago and it has only gotten better since then. I really love it because it can help with written questions and photo questions. Also, it can find study guides that other people have made as well as flashcard sets and practice tests. The free version is also amazing for students who might not be able to afford it. Would 100% recommend
Aubrey
iOS user
Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.😋🩷🎀
Marco B
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. 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 app is phenomenal down to the correct info and the various topics you can study! I greatly recommend it for people who struggle with procrastination and those who need homework help. It has been perfectly accurate for world 1 history as far as I’ve seen! Geometry too!
Paul T
iOS user
Newton's Laws of Motion Explained
U
ur mom sksk
@urmomsksk_sadx
Newton's Laws of Motion form the foundation of classical mechanics, explaining how objects move and interact with forces. These fundamental principles, developed by Sir Isaac Newton, help us understand everything from why objects stay in place to how rockets launch... Show more
Newton's Laws of Motion
Isaac Newton established three powerful laws that explain how objects behave when forces act on them. These laws are the building blocks of physics that you'll use throughout your science classes.
The First Law (Law of Inertia) states that an object at rest stays at rest, and an object in motion stays in motion unless a force acts on it. This explains why you jerk forward when a car suddenly stops—your body wants to keep moving!
The Second Law shows that force equals mass times acceleration . This relationship is directly proportional with force and acceleration but inversely proportional with mass .
Quick Tip: Think of Newton's Second Law next time you're pushing a shopping cart. Notice how it's easier to push an empty cart (less mass) than a full one, even when you apply the same force!
The Third Law tells us that for every action, there's an equal and opposite reaction. When you jump, you push down on the ground, and the ground pushes back up on you with equal force.
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Types of Forces
Forces come in various forms that affect objects differently. Understanding these helps you analyze real-world situations using Newton's laws.
The force of gravity (Fg) pulls objects toward Earth's center and is also known as weight. This universal force keeps your feet on the ground and makes objects fall when dropped.
Normal force (FN) is a contact force that acts perpendicular (at 90°) to the point where objects touch. When you sit on a chair, the chair pushes up on you with normal force to balance gravity.
Friction is the force that opposes motion between surfaces. It's why you can walk without slipping and why your bike eventually stops when you stop pedaling.
Remember: Tension is the force transmitted through cables, strings, or ropes. Next time you see a hanging light or a tow truck pulling a car, you're witnessing tension forces in action!
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Calculating with F=ma
Newton's Second Law gives us a powerful equation to solve real-world problems involving forces, mass, and acceleration.
To find acceleration when you know force and mass, divide force by mass . In Example 1, with a force of 25N applied to a 10kg object, the acceleration equals 2.5 m/s².
When finding mass with known force and acceleration, rearrange the equation to m = F/a. In Example 2, an object experiencing 4,500N of force with 3.0 m/s² acceleration has a mass of 1,500kg.
Problem-Solving Tip: Always check your units! Acceleration should be in m/s², mass in kg, and force in Newtons. Keeping your units consistent prevents calculation errors.
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Free-Body Diagrams
Free-body diagrams are visual tools that show all forces acting on an object, making Newton's laws easier to apply to real situations.
When creating these diagrams, remember that force arrows have both size and direction. Vertical forces typically point up or down, while horizontal forces point left or right. Always label each force clearly (Fg for gravity, FN for normal force, etc.).
A simple example is a book resting on a table. The diagram would show two forces: gravity pulling down and the normal force pushing up. Since the book isn't moving, these forces must be equal.
Drawing Tip: When creating free-body diagrams, start by drawing the object as a simple dot or box, then add force arrows pointing away from the object. Make arrow lengths proportional to force strengths!
Sign up to see the contentIt's free!
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Improve your grades
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Key Physics Vocabulary
Understanding the vocabulary of motion helps you communicate scientific ideas precisely and solve physics problems correctly.
Force is simply a push or pull measured in Newtons (N). Think of force whenever you push a door open, lift a backpack, or kick a soccer ball.
Acceleration means change in velocity over time, measured in meters per second squared . It's not just speeding up—slowing down is negative acceleration! A car going from 0 to 65 mph demonstrates acceleration.
Mass represents the amount of matter in an object, measured in kilograms (kg). It's different from weight—your mass stays the same whether you're on Earth or the moon.
Concept Check: Inertia is an object's resistance to changes in motion. Next time you slam on the brakes and feel yourself lurch forward, you're experiencing inertia in action!
We thought you’d never ask...
What is the Knowunity AI companion?
Our AI companion is specifically built for the needs of students. Based on the millions of content pieces we have on the platform we can provide truly meaningful and relevant answers to students. But its not only about answers, the companion is even more about guiding students through their daily learning challenges, with personalised study plans, quizzes or content pieces in the chat and 100% personalisation based on the students skills and developments.
Where can I download the Knowunity app?
You can download the app in the Google Play Store and in the 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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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
I think it’s very much worth it and you’ll end up using it a lot once you get the hang of it and even after looking at others notes you can still ask your Artificial intelligence buddy the question and ask to simplify it if you still don’t get it!!! In the end I think it’s worth it 😊👍 ⚠️Also DID I MENTION ITS FREEE YOU DON’T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLY❗️❗️⚠️
Thomas R
iOS user
Knowunity is the BEST app I’ve used in a minute. This is not an ai review or anything this is genuinely coming from a 7th grade student (I know 2011 im young) but dude this app is a 10/10 i have maintained a 3.8 gpa and have plenty of time for gaming. I love it and my mom is just happy I got good grades
Brad T
Android user
Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help🤍🤍
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
I found this app a couple years ago and it has only gotten better since then. I really love it because it can help with written questions and photo questions. Also, it can find study guides that other people have made as well as flashcard sets and practice tests. The free version is also amazing for students who might not be able to afford it. Would 100% recommend
Aubrey
iOS user
Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.😋🩷🎀
Marco B
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. 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 app is phenomenal down to the correct info and the various topics you can study! I greatly recommend it for people who struggle with procrastination and those who need homework help. It has been perfectly accurate for world 1 history as far as I’ve seen! Geometry too!
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
I think it’s very much worth it and you’ll end up using it a lot once you get the hang of it and even after looking at others notes you can still ask your Artificial intelligence buddy the question and ask to simplify it if you still don’t get it!!! In the end I think it’s worth it 😊👍 ⚠️Also DID I MENTION ITS FREEE YOU DON’T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLY❗️❗️⚠️
Thomas R
iOS user
Knowunity is the BEST app I’ve used in a minute. This is not an ai review or anything this is genuinely coming from a 7th grade student (I know 2011 im young) but dude this app is a 10/10 i have maintained a 3.8 gpa and have plenty of time for gaming. I love it and my mom is just happy I got good grades
Brad T
Android user
Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help🤍🤍
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
I found this app a couple years ago and it has only gotten better since then. I really love it because it can help with written questions and photo questions. Also, it can find study guides that other people have made as well as flashcard sets and practice tests. The free version is also amazing for students who might not be able to afford it. Would 100% recommend
Aubrey
iOS user
Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.😋🩷🎀
Marco B
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. 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 app is phenomenal down to the correct info and the various topics you can study! I greatly recommend it for people who struggle with procrastination and those who need homework help. It has been perfectly accurate for world 1 history as far as I’ve seen! Geometry too!
Paul T
iOS user