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Dec 11, 2025

4 pages

Dynamics: Understanding Motion and Forces

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Libby

@libby_w

Physics dynamics might seem intimidating, but it's actually about understanding... Show more

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Dynamics
Speed
speed
1
ms, meters per
second
=
distance
time
m
S
Average speed V is over a long period of
time
Speeding
up=
acceleration
A
N

Speed and Motion

Speed is simply how fast something travels, calculated by dividing distance by time measuredinmetrespersecond,m/smeasured in metres per second, m/s. You'll encounter two types: average speed over longer journeys and instantaneous speed at any given moment.

Speed-time graphs tell brilliant stories about motion. A horizontal line shows constant speed, whilst an upward slope indicates acceleration (speeding up) and a downward slope shows deceleration (slowing down). The steeper the line, the greater the change in speed.

Quick Tip: The area under a speed-time graph gives you the total distance travelled - super useful for exam questions!

Understanding these basics sets you up perfectly for tackling more complex motion problems. Speed graphs are your visual tool for making sense of any moving object.

Dynamics
Speed
speed
1
ms, meters per
second
=
distance
time
m
S
Average speed V is over a long period of
time
Speeding
up=
acceleration
A
N

Acceleration Calculations

Acceleration measures how quickly speed changes, calculated using: acceleration = finalvelocityinitialvelocityfinal velocity - initial velocity ÷ time. The units are metres per second squared m/s2m/s², which might look odd but makes perfect sense.

The key equation v = u + at becomes your best friend in physics. Here, v is final velocity, u is initial velocity, a is acceleration, and t is time. You can rearrange this formula to find any missing variable.

In acceleration experiments, you'll use light gates to measure precise timings. The card's width divided by the time gives you velocity at each gate, then you apply the acceleration formula using the time between gates.

Exam Success: Remember that the gradient of a speed-time graph directly gives you the acceleration - no calculation needed!

Dynamics
Speed
speed
1
ms, meters per
second
=
distance
time
m
S
Average speed V is over a long period of
time
Speeding
up=
acceleration
A
N

Newton's Three Laws

Newton's First Law explains that objects hate changing what they're doing. Things at rest stay put, and moving objects keep moving, unless an unbalanced force acts on them. Balanced forces mean no change in motion.

Newton's Second Law gives us the famous equation: Force = mass × acceleration F=maF = ma. This tells you exactly how much force you need to accelerate any object. Heavier objects need more force to achieve the same acceleration.

Newton's Third Law states that every action creates an equal and opposite reaction. When you push against a wall, it pushes back with exactly the same force. This isn't just theory - it's why rockets work and why walking is possible.

Real-World Connection: These laws explain everything from why you wear seatbelts to how athletes push off starting blocks!

Dynamics
Speed
speed
1
ms, meters per
second
=
distance
time
m
S
Average speed V is over a long period of
time
Speeding
up=
acceleration
A
N

Weight, Mass and Terminal Velocity

Don't confuse mass (amount of matter, measured in kg) with weight (force due to gravity, measured in Newtons). Weight equals mass times gravitational field strength W=mgW = mg, where Earth's gravity pulls at roughly 10 N/kg.

Terminal velocity happens when falling objects reach maximum speed. Initially, weight pulls down whilst air resistance pushes up. As speed increases, air resistance grows stronger until both forces balance perfectly.

At terminal velocity, acceleration becomes zero because the forces are balanced. This explains why parachutists don't just keep getting faster and faster - they reach a steady falling speed.

Key Insight: Terminal velocity depends on the object's shape and size - that's why feathers fall slower than stones in air!



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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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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

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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

 

Physics

68

Dec 11, 2025

4 pages

Dynamics: Understanding Motion and Forces

user profile picture

Libby

@libby_w

Physics dynamics might seem intimidating, but it's actually about understanding how things move around you every day. From cars accelerating down the street to objects falling through the air, Newton's laws explain the motion you see everywhere.

Dynamics
Speed
speed
1
ms, meters per
second
=
distance
time
m
S
Average speed V is over a long period of
time
Speeding
up=
acceleration
A
N

Sign up to see the contentIt's free!

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Join milions of students

By signing up you accept Terms of Service and Privacy Policy

Speed and Motion

Speed is simply how fast something travels, calculated by dividing distance by time measuredinmetrespersecond,m/smeasured in metres per second, m/s. You'll encounter two types: average speed over longer journeys and instantaneous speed at any given moment.

Speed-time graphs tell brilliant stories about motion. A horizontal line shows constant speed, whilst an upward slope indicates acceleration (speeding up) and a downward slope shows deceleration (slowing down). The steeper the line, the greater the change in speed.

Quick Tip: The area under a speed-time graph gives you the total distance travelled - super useful for exam questions!

Understanding these basics sets you up perfectly for tackling more complex motion problems. Speed graphs are your visual tool for making sense of any moving object.

Dynamics
Speed
speed
1
ms, meters per
second
=
distance
time
m
S
Average speed V is over a long period of
time
Speeding
up=
acceleration
A
N

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

Acceleration Calculations

Acceleration measures how quickly speed changes, calculated using: acceleration = finalvelocityinitialvelocityfinal velocity - initial velocity ÷ time. The units are metres per second squared m/s2m/s², which might look odd but makes perfect sense.

The key equation v = u + at becomes your best friend in physics. Here, v is final velocity, u is initial velocity, a is acceleration, and t is time. You can rearrange this formula to find any missing variable.

In acceleration experiments, you'll use light gates to measure precise timings. The card's width divided by the time gives you velocity at each gate, then you apply the acceleration formula using the time between gates.

Exam Success: Remember that the gradient of a speed-time graph directly gives you the acceleration - no calculation needed!

Dynamics
Speed
speed
1
ms, meters per
second
=
distance
time
m
S
Average speed V is over a long period of
time
Speeding
up=
acceleration
A
N

Sign up to see the contentIt's free!

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Improve your grades

Join milions of students

By signing up you accept Terms of Service and Privacy Policy

Newton's Three Laws

Newton's First Law explains that objects hate changing what they're doing. Things at rest stay put, and moving objects keep moving, unless an unbalanced force acts on them. Balanced forces mean no change in motion.

Newton's Second Law gives us the famous equation: Force = mass × acceleration F=maF = ma. This tells you exactly how much force you need to accelerate any object. Heavier objects need more force to achieve the same acceleration.

Newton's Third Law states that every action creates an equal and opposite reaction. When you push against a wall, it pushes back with exactly the same force. This isn't just theory - it's why rockets work and why walking is possible.

Real-World Connection: These laws explain everything from why you wear seatbelts to how athletes push off starting blocks!

Dynamics
Speed
speed
1
ms, meters per
second
=
distance
time
m
S
Average speed V is over a long period of
time
Speeding
up=
acceleration
A
N

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

Weight, Mass and Terminal Velocity

Don't confuse mass (amount of matter, measured in kg) with weight (force due to gravity, measured in Newtons). Weight equals mass times gravitational field strength W=mgW = mg, where Earth's gravity pulls at roughly 10 N/kg.

Terminal velocity happens when falling objects reach maximum speed. Initially, weight pulls down whilst air resistance pushes up. As speed increases, air resistance grows stronger until both forces balance perfectly.

At terminal velocity, acceleration becomes zero because the forces are balanced. This explains why parachutists don't just keep getting faster and faster - they reach a steady falling speed.

Key Insight: Terminal velocity depends on the object's shape and size - that's why feathers fall slower than stones in air!

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.

Most popular content: Acceleration

Most popular content in Physics

Most popular content

English - inspector calls quotes and analysis

Quotes from every main character

English LiteratureEnglish Literature
10

Can't find what you're looking for? Explore other subjects.

Students love us — and so will you.

4.9/5

App Store

4.8/5

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

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