Newton's Laws: Crash Course Physics #5 

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My favorite explanation of Newtons laws comes from my high school Physics teacher: 1.) Stuff is hard to shake 2.) More stuff is harder to shake 3.) Stuff pushes back

"Now the normal force isn't like most other forces. It's special." so much for normal.

A student in bed will remain in bed until acted upon by a large enough panic : The lesser known Newton's 4th Law.

Newton's Laws of Motion: 0:53 - First Law (Inertia): "An object in motion will remain in motion, and an object at rest will remain at rest, unless acted upon by a force." 1:37 - Second Law (Fn = ma): "Net force is equal to mass times acceleration." 3:40 - Third Law (Equilibrium): "For every action, there is an equal but opposite reaction." 4:52 - Further explanation on Normal Force and Tension Force

When your physics final is tomorrow and you tryna learn everything the night before... 😂😂😂

Newton slaps top of car. Car slaps newton back. Equal and opposite force!

"There will be no Christmas without physics" *Reindeer flies with sleigh* (Defies physics)

I've gotta say, after watching this series so far, I'm happy they have Dr Somara as the host. Her voice is nice to listen to, and her delivery of the material is engaging. I had to study basic wavelength physics in college for part of my Speech Pathology degree, and I found the course to be a bit dull. I wonder how it will be if and when they discuss it here.

The arrangement of the Rubik's Cube in this episode is still exactly identical to its arrangement from last episode. Unfortunately, this means that no one is even trying to work on it in between episodes. This just isn't right. Whenever you see an unsolved Rubik's Cube sitting around, fixing it should always be a top priority.

"Suppose you threw a 5kg ball up in the air, and then, you know, got out of the way because that could really hurt if it hits you." This is easier to understand than I thought it would be.

these crash course people are great teachers! much better than the ones in my personal experiences at least...

5:01 just completely clarifies my confusions in physics after 5 years.

Stop scrolling through the comments and actually listen to the dang video

I can tell im going to watch this video at least 3 more times

I have this weird habit where I like to watch all these education physics videos after a physic exam....why....

"And for that we're gonna turn to a physicist you've probably heard of" Me: BILL NYE THE SCIE....Oh.

I cant focus on the video because of my habit reading the comments while watching😂

I was getting it until the elevator thing ...

I love her accent, not gonna lie. Especially how she says equilibrium :3

@CrashCourse I'm loving the Physics course and they are helping me so much. You teach better than in the school I was. I'm watching many times to get every point. Thank you for sharing these knowledges with us.

The thought bubble about the hockey rink wasn't timed well. It showed constant motion when Shini was talking about acceleration, and stopped the puck when Shini was talking about equilibrium. This might really confuse people who are learning this for the first time.

Sir Isaac Newton: For every action, there is an equal opposite reaction Hamilton fans: *screams in 13 different languages*

Thank you for taking the time to make these videos. I'm having a terrible time with my current professor and this has already helped! Godspeed!

Have a physics midterm tomorrow. Hopefully these help

My physics final is tomorrow. Wish me luck, I'm going to need it lmao

British accents give me joy whenever I hear them, bless the British.

Eeeeeh, I have an issue with how you describe the reason that the action and reaction forces don't cancel out. It is less about the difference between the sleigh vs the force on the ground and more about the fact that the forces are acting on different objects. Consider an astronaut pushing another astronaut in the depth of space. Each astronaut experiences an equal and opposite force, and there are NO OTHER FORCES acting on them, yet they still accelerate. Why? Because while the forces are equal and opposite, they are acting on _different objects_. You can pick up the mug, in spite of the equal and opposite reaction force, because the reaction force isn't acting on the same object. If force 1 is on object A, and force 2 is on object B, the fact that they're equal and opposite is irrelevant. They can't cancel if they're acting on different objects. The action force is object A acting on object B, the reaction is object B acting on object A. Each of these forces is free to induce acceleration on their respective objects.

when corona makes you watch these videos.

1:25, I know this is a serious topic, but I just found it funny.

Thank you for posting this!! I have been studying to get into the Navy and I am on the Physical Science chapter. I have a better understanding by watching things in motion and film, and this video has helped a lot!!! :)

This is wonderful! I was waiting for this for such a long time.. Could you do some videos about electronics and stuff like that? Keep up the good work!

I've learned more in this video than in my physics class all year.

Thanks for the upload! I'd like to see more of Shini, her accent is wonderful to listen to, she has a beautiful smile and she holds attention well

The quality of your videos are amazing, and also interesting! Thank you.

Remember the PBS show "Mechanical Universe" in the 70s? They also did the moving parts of the equation. But they had little starbursts when factors canceled each other out.

Newton's 4th Law of Motion - "A Rubik's cube at unsolved position will continue to be in unsolved position unless it is acted upon by a external effort to change its state of being."

5:52 The teacher says: There would be no Christmas without physics. Me: Why he doesn't put a flying reindeer?

Most interesting video so far. It's nice to see the notions/concepts build up piece by piece. Still, so many ways to describe the same "event" and it's all down to mathematics.

One does not simply "Throw" a 5kg bowling ball...

These videos are pretty helpful so far, but the timing was honestly bad, you guys should've started earlier since that the AP Physics exam will be next week.

Hey Shini! I'm having my physics exam tomorrow and these videos really help! Keep going! 😊

I skipped a huge part of my math book that talked about this stuff. when finals came i had to learn EVERYTHING in one night. this video helped a lot much love.

Her:no Christmas without physics Santa: are you sure about that

Thanks for being a grade teacher. My irl teacher can’t teach.

Well I was like, "Let me watch some easy physics to procrastinate for this physics exam today". Then I realized how much basic physics I've forgotten... Well now I know why people hate physics so much...

special appearance:professor Feynman!!!

G in Olevels = 10m/s G in ALEVELs = 9.81 m/s

How is it that I learn more in the night before a test from a woman I don't personally know than I do from my teacher! Thank you everybody at Crash Course!

I like how this is posted for me to revise for my physics test next week. Good timing!

There would be no christmas without physics. *Holds up a finger* ... *Slowly pulls it back*

I love learning in my free time. Thanks for the videos! I'm about to start college, and these videos have definitely helped refresh my memory about what I've learned in high school while keeping me entertained by presenting new additional info.

newtons 3rd law example: a gun fires, there is a recoil

that example at the end was confusing asf. Wouldn't it be better to start off with just 3 units for a CRASH COURSE instead of going straight to elevators and tension forces?

I have one question.... How did that guy at 1:24 not shatter his foot?!?!?!

Crash Course Engineering Next !?!?!?

This video cleared up a lot of things for me! Thank you for making this show!

I will never forget “Every action has an equal opposite reaction” thanks to Hamilton but at the same time i will never not sing that line.

thank you so much for making this wonderful video free!!

No Christmas without physics...I-

8:32 isnt that Newton's Second law?

Gosh i think I learn more in RU-vid than my teacher's stuffs thinks that she knows too much while she was fooling us around"LOVE U YOU TUBE TEACHERS"got to understand alot

This is a really odd way of handling the weight-counterweight example, considering the forces are linked. Gravity pulls both the weight and counterweight "down" with the same force while the lift and counterweight pull each other up by their own weight. Basically, the force acting on the lift is its own mass * gravity - the counterweight's mass times gravity, isn't it? All the rope and pully system does (assuming no stretching or friction) is to redirect the counterweight's weight up relative to the lift's weight, almost as though it were attached to a balloon, instead. I've done calculus and analytical physics in the university and your approach to jamming everything in the same colossal equation still confuses me greatly. It just seems so much simpler to take the maths step by step in what I presume is intended to be an introductory course in physics for people who haven't already studied physics. There are simpler ways to explain this.

this genuinely might be the only reason i pass physics, thankyou so so much!!

i love these ppl on this channel sm they give me hope in my school life

0:40 Snake? Solid Snake? Man, I did not expect to see him during Physics class.

It's my first time checking out the physics crash course and Shini does a great job. Some of the other people get a little too hyperactive and confusing. This was perfect.

8:50 It's quite confusing that the Tension Force on the counterweight is drawn smaller than the one on the elevator, since these should be equal as they are in the equation. This Force should be larger than the Gravitational Force since it is accelerating upwards. I know it's just an illustration but it might still confuse a lot of people.

love these vids, helping me through college one at a time! thanks for all that you folk at crash course do!

I have a question. Does Newton's 3rd law also apply to like when, you hit someone who's kinda stronger than you so you can feel the impact as well.

Newtons 4th law of motion: every book will be covered in dust unless and until and exteral exam acts on it😂😂

"There will be no Christmas, without Physics "😄

Elevator > Lift. Elevators change your elevation. Lift should only go upward.

I just like how she is explaining physics with such a smiling face i start loving phy but my finals r near i should have discover this early

yesss her videos are getting so much better! great explaining! great visuals!

When the magnitude of Fg and Ft are both 5 Newtons, should Fg be written as -5 instead of 5 so they add up to zero?

+CrashCourse Great video Chrash; however, I can't wait to see your up-coming video on relativity where we learn that gravity isn't actually a force but the curvature of space-time.

At 1:23 I was dying of laughter 😂😭 I was watching this in class (everyone) and was the only one that was laughing .

+CrashCourse This is so informative! I love your channel! What software did you use? Thanks for making such great videos!

Excellent presentation. Thanks for being more organized and slowing down the talking.

this was rlly useful I hopefully I will ace my physics force test cause its today

At 8:23, isn't the force of tension the same as the force of gravity on the counterweight ? I mean Ft = m(c).g It's Just the only thing that i don't understand.

Laws of motion do not work, My crush atracts me but I do not atract her. :)

I really like watching these before the lecture on the topic.

Thank you for this video! It helped sooo much, I'm a fifth grader trying to learn the order.

"F"ull = "M"etal "A"lchemist

3:40 - "...which is explained by Newton's third law... that's what we call the normal force." ...what? No, it isn't. Where gravity's concerned, the reaction force is the Earth being pulled. I'm not totally sure what the normal force's reaction is - I think it has to do with the stress on different parts of the object - but I know that when it comes to gravity, the reaction will always be the force on the other body, and the fact that the normal force is also equal and opposite in this case is a consequence of the fact we're considering a stationary object, not Newton's third law.

Thank you for being such a great teacher I hope you keep on making greater videos

these videos are great and all but I really just enjoy listening to her talk

That was quite the complicated method. Also could be done by just calculating the resultant force by multiplying the total mass of contents in the elevator by gravity and subtract the mass of the counterweight also multiplied by gravity to find the resultant force. Since we know the total mass of all bodies in the system calculating to be the mass of the counterweight plus the mass of the elevator we can divide the resultant for the system by the total mass to find acceleration.

In before thumbnail.

except thats not how equal and opposite reactions work! When you push on an object, its not the object pushing you back, its YOU pushing you back! In space, this is easily demonstrated because if you have two objects, floating side by side, and object A pushes on object B, they fly apart at half the force of the push, in opposite directions. Object B has not acted on object A, Object A has done all the force applying, but because nothing is stopping it from going in the opposite direction, like say the ground, or gravity, its force is applied equally between the objects, in equal, but opposite directions! Its still the "normal force" but its not the table pushing on your finger, its your finger pushing on your hand! Where things get tricky is when Object A and B have unequal masses, because if Object B is twice the mass, it doesnt receive as much acceleration, and effectively Object A pushes off of Object B, but it still causes Object B to drift off In the opposite direction! (just by a quarter the amount) Or, lets say Object A has a rocket, that lets it push against Object B, without getting pushed in the opposite direction, then something similar to what you described happens, because Object B was at rest, it resists change in acceleration, relative to its mass, it will attempt to squish Object A between the rocket and itself, until the rocket has applied enough force that it has the same velocity as Object A, its change in velocity becoming zero, as it is in space, and no other force is acting on it, it will then be in You guessed it, equilibrium! Like seriously guys, was i the only one that learned this from space first, and earth second? Also, fun fact, every time we launch something from the earth to space, we effectively slow the rotation of the earth by a smidge. It also happens any time we do a gravity assist around the moon, or another planet, or ourselves, we infinitesimally change the rotation period of the earth/moon/planet in question.

When you sleep in class, so you end up watching this at night trying to do homework

Got an Ap Physics Exam today and I decide to watch these the morning of

Who needs notebooks when you have CrashCourse? I have a test on this in 4 days but I don't even look at what we have learned in class, I don't need it, I got Shini

8:32 *Second law Not first law (Inertia)

I'm in love with Shini!

Her esses are clipping so hard please do something about it CrashCourse!

I forget the whole thing. My rise was approximately at the beginning. What a remarkable creature. So well spoken.

Okay, this is the first explanation of normal force that makes sense to me. Thank you!