Newton's First Law of Motion, also known as the Law... Show more
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0
D
Demi Zenit
11/21/2025
AP Physics 1
Newton's First Law of Motion
185
•
Nov 21, 2025
•
Understanding Newton's First Law of Motion
D
Demi Zenit
@demizenit_ftbu
1 / 10
Newton's First Law of Motion
Newton's First Law of Motion forms the foundation of classical physics and helps explain why objects move the way they do. This law will help you understand many everyday situations, from why you need seatbelts to why it's harder to start moving than to keep moving.
You'll soon discover how this simple principle affects nearly everything around you!
Law of Inertia Explained
Newton's First Law states: An object at rest will stay at rest, and an object in motion will stay in motion at constant velocity, unless acted upon by an unbalanced force.
This means that things naturally resist changes in their motion. A ball sitting on the ground won't suddenly start rolling by itself. Similarly, a ball rolling across the floor would keep rolling forever if nothing stopped it.
Think About It: Every time you push something to get it moving or use brakes to stop, you're overcoming inertia!
Understanding Motion
Motion simply means a change in an object's position over time. When you see cars driving down the street, they're in motion because they're changing position relative to their surroundings.
Motion is all around us—from planets orbiting the sun to atoms vibrating in place. Even when you walk to class, you're demonstrating the principle of motion by changing your position.
You can easily observe motion by tracking an object's position at different times.
What Is Force?
A force is any push or pull acting on an object. Forces cause objects to start moving, stop moving, or change direction.
Forces are everywhere in your daily life. When you kick a soccer ball, you apply a force. When you pull open a door or push a shopping cart, you're using force.
Remember: Forces don't have to come from living things—gravity, magnetism, and electricity are all forces too!
Inertia in Action
Inertia is the resistance an object has to changes in its motion or velocity. It's why the cookies on the plate won't move unless you apply a force to them.
The more mass an object has, the greater its inertia. This is why it's easier to push an empty shopping cart than a full one—the full cart has more mass and therefore more inertia.
Objects at rest tend to stay at rest because of their inertia. This is why you need to apply force to start moving objects that aren't already moving.
Inertia in the Air
Once an object is airborne, it would theoretically continue moving forever if no forces acted upon it. This is why objects in space can travel for billions of miles!
On Earth, airborne objects eventually stop because forces like gravity pull them down, and air resistance slows them. Without these forces, a thrown baseball would never come down or slow down.
The next time you throw something, imagine how it would move if there were no gravity or air to affect it.
Constant Velocity
According to Newton's First Law, a moving object like this skater would continue at the same speed and direction (velocity) forever if no unbalanced forces acted on them.
In reality, forces like friction from the ice and air resistance gradually slow the skater down. Without these forces, the skater would glide endlessly at the same speed.
Cool Fact: Astronauts in space experience this principle directly—once they start moving in a direction, they continue until they push against something to change course!
Speed, Velocity, and Acceleration
Speed measures how much distance an object covers in a certain amount of time (like 60 mph). It's calculated using the formula: Speed = Distance ÷ Time.
Velocity includes both speed AND direction—so "60 mph north" is a velocity. Two cars might have the same speed but different velocities if they're heading in different directions.
Acceleration happens when velocity changes—either speeding up, slowing down, or changing direction. When you press the gas pedal, you're accelerating; when you hit the brakes, you're also accelerating (negatively).
The Mystery of Slowing Objects
You might wonder: If objects in motion should stay in motion, why do rolling balls and sliding books eventually stop without anyone touching them?
The answer is friction—an invisible force that opposes motion when surfaces contact each other. When you slide a book across a table, friction between the book and table gradually slows it down until it stops.
This invisible force is present in almost every movement on Earth, which is why perpetual motion machines are impossible to build.
Earth vs. Space Motion
Objects on Earth behave differently than objects in space because Earth is full of friction, while space is nearly frictionless.
The moon continues its orbit around Earth at a constant speed because there's virtually no friction in space to slow it down. Meanwhile, a rolling ball on Earth quickly comes to a stop due to friction with the ground and air.
Imagine This: If you could eliminate all friction, a single push could send an object moving forever!
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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
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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
Understanding Newton's First Law of Motion
D
Demi Zenit
@demizenit_ftbu
Newton's First Law of Motion, also known as the Law of Inertia, is one of the fundamental principles that explains how objects behave when forces act upon them. This law helps us understand why objects stay at rest or in... Show more
Newton's First Law of Motion
Newton's First Law of Motion forms the foundation of classical physics and helps explain why objects move the way they do. This law will help you understand many everyday situations, from why you need seatbelts to why it's harder to start moving than to keep moving.
You'll soon discover how this simple principle affects nearly everything around you!
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Law of Inertia Explained
Newton's First Law states: An object at rest will stay at rest, and an object in motion will stay in motion at constant velocity, unless acted upon by an unbalanced force.
This means that things naturally resist changes in their motion. A ball sitting on the ground won't suddenly start rolling by itself. Similarly, a ball rolling across the floor would keep rolling forever if nothing stopped it.
Think About It: Every time you push something to get it moving or use brakes to stop, you're overcoming inertia!
Sign up to see the contentIt's free!
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By signing up you accept Terms of Service and Privacy Policy
Understanding Motion
Motion simply means a change in an object's position over time. When you see cars driving down the street, they're in motion because they're changing position relative to their surroundings.
Motion is all around us—from planets orbiting the sun to atoms vibrating in place. Even when you walk to class, you're demonstrating the principle of motion by changing your position.
You can easily observe motion by tracking an object's position at different times.
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What Is Force?
A force is any push or pull acting on an object. Forces cause objects to start moving, stop moving, or change direction.
Forces are everywhere in your daily life. When you kick a soccer ball, you apply a force. When you pull open a door or push a shopping cart, you're using force.
Remember: Forces don't have to come from living things—gravity, magnetism, and electricity are all forces too!
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Inertia in Action
Inertia is the resistance an object has to changes in its motion or velocity. It's why the cookies on the plate won't move unless you apply a force to them.
The more mass an object has, the greater its inertia. This is why it's easier to push an empty shopping cart than a full one—the full cart has more mass and therefore more inertia.
Objects at rest tend to stay at rest because of their inertia. This is why you need to apply force to start moving objects that aren't already moving.
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Inertia in the Air
Once an object is airborne, it would theoretically continue moving forever if no forces acted upon it. This is why objects in space can travel for billions of miles!
On Earth, airborne objects eventually stop because forces like gravity pull them down, and air resistance slows them. Without these forces, a thrown baseball would never come down or slow down.
The next time you throw something, imagine how it would move if there were no gravity or air to affect it.
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Constant Velocity
According to Newton's First Law, a moving object like this skater would continue at the same speed and direction (velocity) forever if no unbalanced forces acted on them.
In reality, forces like friction from the ice and air resistance gradually slow the skater down. Without these forces, the skater would glide endlessly at the same speed.
Cool Fact: Astronauts in space experience this principle directly—once they start moving in a direction, they continue until they push against something to change course!
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Speed, Velocity, and Acceleration
Speed measures how much distance an object covers in a certain amount of time (like 60 mph). It's calculated using the formula: Speed = Distance ÷ Time.
Velocity includes both speed AND direction—so "60 mph north" is a velocity. Two cars might have the same speed but different velocities if they're heading in different directions.
Acceleration happens when velocity changes—either speeding up, slowing down, or changing direction. When you press the gas pedal, you're accelerating; when you hit the brakes, you're also accelerating (negatively).
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The Mystery of Slowing Objects
You might wonder: If objects in motion should stay in motion, why do rolling balls and sliding books eventually stop without anyone touching them?
The answer is friction—an invisible force that opposes motion when surfaces contact each other. When you slide a book across a table, friction between the book and table gradually slows it down until it stops.
This invisible force is present in almost every movement on Earth, which is why perpetual motion machines are impossible to build.
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Improve your grades
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By signing up you accept Terms of Service and Privacy Policy
Earth vs. Space Motion
Objects on Earth behave differently than objects in space because Earth is full of friction, while space is nearly frictionless.
The moon continues its orbit around Earth at a constant speed because there's virtually no friction in space to slow it down. Meanwhile, a rolling ball on Earth quickly comes to a stop due to friction with the ground and air.
Imagine This: If you could eliminate all friction, a single push could send an object moving forever!
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