Newton's laws of motion - physics explained
Another week and another great time for some fun science. This time, I will do a post about one of the easiest things in physics. Why the easiest? Because I managed to explain this to kids in kindergarten. It is interesting and it is one of those topics that is always somewhere around us and in everything we do. Before we start, here is the list of previously published posts in my physics explained series:
DOPPLER EFFECT
COLD BOILING WATER
HOW DO WE SEE COLORS
LEARN ABOUT RAINBOWS
EVERYTHING IS MAGNETIC!
DIFFERENCE BETWEEN HEAT AND TEMPERATURE
CALCULATE THE SPEED OF LIGHT USING CHOCOLATE
To understand what this post will be about, you do not need any previous knowledge or understanding of physics, I will try to get you familiar with everything that is important and I will try to make it as simple and as fun as possible. Are you ready? Let's go!
After Isaac Newton studied Descartes, he put all that knowledge to good use and not only used his law of inertial motion but developed it further and came up with two additional ones that were his own. Even though Sir Isaac Newton is famous for these 3 laws, that is not everything he has done for physics and mathematics. His work resulted in integral and differential calculus and the first reflecting telescope. FUN FACT: he was born on Christmas and many fun-oriented scientists celebrate that date. Remeber my posts about light? Newton was the one who studied how white light goes through a glass prism and explained how it contains all the other colors in it. We have a measurement unit for force named in his honor.
There is, of course, that famous story with an apple falling on his head that led him to gravity but let's get back to those 3 laws we will be talking about here. He described all 3 of those laws in "The Mathematical Principles of Natural Philosophy," which was published in 1687. We will explain the laws one by one and if you are interested in learning more, there will be a reference list at the end of the post for you to check out.
The law of inertia was first formulated by Galileo Galilei and was later generalized by René Descartes. Newton finished it off and explained it in a way we know today. This law states that if a body is at rest or moving in a straight line at constant speed, it will continue to do so as long as there is no outside force. The easiest way to explain this law to a 3-year-old is to say:
If you do not change it, it will not change.
We have two possible situations here, with a body at rest and with a body moving at a constant speed. Both situations include the lack of outside force to change them. Without anything "getting in the way" the body will remain in its state. It will not change what it is currently doing.
a) if a body is at rest, it will stay at rest if the outside force acting on it is zero
b) if a body is in motion, it will stay in motion if the outside force acting on it is zero
Now, what do I mean when I say "the outside force on it is zero"? Imagine a rock, a large enough rock for you to push. The rock is standing still, it is not moving. This is because the outside force on it is zero, no one is touching it and forcing it to move. Now imagine that you are on one side of it pushing it forward and your friend is on the other side pushing it forward. If you and your friend are both pushing the rock in the opposite direction and with the same exact force, the rock will not move an inch. Why? Because the forces will cancel each other out and the net force on the rock will be zero.
So there are two ways to have the net force at zero. You can have no force at all acting on the body (DO NOT TOUCH IT) or the adding up of all forces will amount to zero (FORCES WILL CANCEL EACH OTHER OUT). So there you go, that is the first law, aka the law of inertia. If you do not change the motion of a body, the motion of the body will not change. Pretty simple philosophy, right? No wonder the kids in kindergarten understand this principle. Let's review the law one more time and state it precisely:
Newton's 1st law - law of inertia:
When a body is at rest or moving at a constant speed and the net force on it is zero, the body will not change its behavior.
Ok, so far we have covered what happens (not happens) when we are not doing anything to the body or doing something in a way that the net force is zero. Now we will continue this story by adding the force to the mix. What happens to an object that is standing still if I start pushing it? It starts moving. Again, pretty simple, right? This is how you can explain it to a 3-year-old:
If you change it, it will change.
Newton's second law is bringing us acceleration. Acceleration is the change of speed. When a body is at rest, the speed is zero and when you start using a force on it, you will push it to start moving. You will change its speed from zero to something and that change is called acceleration. How did the body change its speed? By having a force different than zero acting on it.
To cause an object to accelerate (change its speed) we have to apply a force. The more force we apply, the bigger that acceleration will be and if we apply the same force on two objects the lighter one will accelerate more. These are the two things acceleration depends on, mass and force.
You probably can not pick up an elephant and change its speed but you can pick up a toy elephant. This is because the mass of an object plays an important role. The greater the mass is, the smaller the acceleration will be.
Acceleration and mass are inversly related.
Acceleration decreasses as the mass increases.
Forget about the elephant, try pushing a car. You probably can not make it move but there are people who can. Those strong people are applying a greater force on the car and it will start moving. The greater the force, the greater the acceleration will be.
Acceleration and force are directly related.
Acceleration increases as the force increases.
Let me share with you what makes me extremely angry... People saying that Newton's second law is something that it's actually not. This is NOT the equation of Newton's second law:
NOOOOOO !!!!
There is nothing wrong with using this formula but that is not the formula of this law! By saying this is the formula you are saying that the force is caused by mass and acceleration and IT IS NOT! The acceleration is not causing the force to appear LOL, the force is generating acceleration. Trust me, I have studied physics and if you said this was the Newtons second law on your exams, you would flunk that test. This is considered a huge mistake in your thinking pattern because acceleration is not producing force, the force is producing acceleration and the only correct formula for the Newtons second law is:
If you apply a force (measured in Newtons) to a mass (measured in kilograms), that mass will develop acceleration (measured in meters per second per second). Ok, I have taken a few deep breaths and calmed down, we can continue now and review this law precisely:
Newton's 2nd law - acceleration:
The acceleration of an object depends directly upon the net force acting upon the object, and inversely upon the mass of the object.
We are almost done. The only thing that is left for us to do is to explain the third law, also known as the law of action and reaction. For some reason, people seem to have the most trouble with this one but not the kids. Oh no, that 3-year-old will get it with no problem, here is what you need to say to him:
When you change it, it changes you too.
Newton's third law explains how every action will have a certain reaction as a result. That reaction will be the same in its magnitude but opposite in its direction and is one of the reasons why your joints hurt when you run. You can not apply a force on an object without feeling that force on yourself too.
Imagine you are pushing a wall and applying great force on it. Nothing is happening, you can not move the wall. Now imagine that you are pushing it with the same force but you are wearing rollerblades on your feet. What happens? You are pushed back from the wall. The wall did not push you, or did it? Yes, it did. The same thing happens when you are getting out of a boat or fireing a gun. It happens whenever you hit something and feel the pain. There is always a force acting upon you that is the same as the one you were acting with upon something.
Let's review this law and state it precisely:
Newton's 3rd law - action and reaction
Whenever two bodies interact, they apply forces to one another that are equal in magnitude and opposite in direction.
And there you go, now you know Newton's 3 laws of motion and you can easily explain them to a 3-year-old. The sentences you can use are these:
- If you do not change it, it will not change.
- If you change it, it will change.
- When you change it, it changes you too.
As for yourself, if you have any questions, as always, I am here for you and you can check out these references too:
Newtons laws of motion
How Newtons laws of motion work
Newtons laws
Until next time,
KEEP YOUR SMILE ON
and respect your inner genius!
If you are interested in something physics (or science in general) related, tell me and I would be happy to make a post about it and explained it. Promoting science and making it understandable gives me great joy, I would be happy to help you.
Image sources:
- cover image is from pngtree.com and royality free, you can check it out here
- clipart in my titles is from Free Clipart Library
- Image of Newton is from Free Clipart Library
- blue car image is from quora.com and can be foundhere
- two people pushing rock is from testeach and ce be found here
- green car image is from googlephysics.blogspot.com and can be found here
- the image with the wrong formula is from physics4kids.com and can be found here
- the image with the correct formula I made myself
- the bitmoji is well... my bitmoji. Get yours at https://www.bitmoji.com/
- clipart in my titles is from Free Clipart Library
- Image of Newton is from Free Clipart Library
- blue car image is from quora.com and can be foundhere
- two people pushing rock is from testeach and ce be found here
- green car image is from googlephysics.blogspot.com and can be found here
- the image with the wrong formula is from physics4kids.com and can be found here
- the image with the correct formula I made myself
- the bitmoji is well... my bitmoji. Get yours at https://www.bitmoji.com/
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Isaac is one of my main man! The more you know about him, the more he is fascinating.. Thanks for sharing a bit of knowledge <3 <3 <3
If you're interested, write about Deja Vu :P :D ( I never researched that)
Hmmmm, interesting, Deja Vu... very interesting 💚
Genius. Srsly. So, tell me, what is your IQ? Is there anything you can't write about knowledgeably? Was physics your major in college? Are you schizophrenic? Physics on one side; metaphysics on the other. You're about to give me a complex. (Do you really want that on your conscience?)
I refuse to tell my IQ to people, I consider that a private information :D Physics was my major, yes. I am not schizophrenic and I do not want to give you a complex. I just have a freaky brain that I have spend years on training to use both left and the right side. This was the funniest comment I have ever received by the way, thank you for making me laugh honey! I love you so much! 💚
See, this is why I never took physics. Stuff like this makes my throat close up. I can remember the simple basics:
#1 = A body in motion tends to remain in motion; a body at rest tends to remain at rest.
#2 = Force equals mass times acceleration. (But then you start quibbling over the math and I just want to go (##$#)@&#$(*%)!!
#3 = For every action there is an equal and opposite reaction.
That's all the physics I want to know. Now leave me alone.
And that is all correct, not precise but still correct! Good for you, I am leaving you alone now :D
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TrufflePigTrufflePig, Sweetie. You and I, we've got a problem. This post is worth at least 3 times your appraisal and should be somewhere in the top 5. 135 votes is about right, I'd say. I'll go along with that. 135 decent votes, that is. Not these piddly little $.00 curation trail trifles.
However, 1 out of 3 is not a passing grade. Don't make me sell you for bacon. [grin]
@zen-art
lolololololol
And yes, after I have read that 17 number I was little disappointed too :D
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Thank you 💚💚💚
Holy Cow! I was out on the road testing and confirming all of Ike's rules and theories and would have missed this if not for SteemEngine. Another reason to be grateful to them.
That was as concise and well written as anything I have ever read on the subject (s). Amazing post sister. Thank you.
Thank you, I am very pleased to hear that and I will take that as one of the biggest compliments I have ever received 💚
You making physics so simpme with such clear detailing...though i am not a science background...now it seems quite familiar
The point was to make it easy to understand and follow along. I am glad I was able to achieve that 💚
I love the way you combine physics with art! Definitelty brings it to life. Newton's third law – I suppose that's what pilates resistance bands are all about.
YES! A lot of exercises are based on that law actually :)
Ha ha, if you are going to get nit picky about the form of the second law, isn't it originally a link between impulse and the application of force over a period of time. (in not sure how to do formulas in markdown... So words will have to do...).
J = int F dt
Which is essentially the a = F/m form, but if you go one step...
I love that I am nit picky and I love it even more when someone is more nit picky than me LOL :D :D :D
I think you have answered your own question there honey, change of impulse is a product of application of force, not the other way around. 💚
I can't wait for the gravity explanation now that I have read these. My mind works like a child's quite often so I was able to follow along,
Oh gravity, that is a tough one lol, many great scientists are still trying to figure that one out so I am not sure I will succeed. It would be nice though, I think if I was able to explain gravity there would be a Nobel prize in it for me :)
I can explain it very easily, it wouldn't win a Nobel prize by any means though. It is a figment of some folks imagination.
You did spark my interest and I would love to hear your explanation, there is a Nobel prize in it for you yet, you never know.