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Isaac Newton physics genius brilliant inventor..weird dude

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let's get started.... I want to introduce you to my buddy

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Isaac [Apple introducing Isaac Newton]

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Isaac Newton....... okay okay Sir Isaac Newton sorry he's a little [Newton watering his plants]

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touchy about pretty much everything we're not going to sugarcoat it Isaac

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Newton would have been something of a big annoying rude but he's also one of

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the smartest most important physicists mathematicians and inventors the world

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has ever known the next few units are going to look at

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his laws of motion which are the underpinning of a whole lot of physics [Man rides by on a bicycle]

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stuff so we think it's only proper for us to give you a sense of who old Ike

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here really was don't worry in a few years when everyone finally acknowledges

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your genius we'll do a big biography on you too and we're sure we'll be able to

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talk about how sweet and kind you are too but look maybe we're being too hard [Apple discussing isaac newton as a baby]

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on Sir Isaac, he didn't have the happiest childhood after all he was born in 1643

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in Woolsthorpe which is in jolly old England

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his father died before baby Isaac was even born and when Ike was just a

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toddler his mother left him with his grandma and married another dude...That [Isaac's mum hands Ike to Grandma and walks away]

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action left Isaac with some abandonment issues which makes sense and left him

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feeling pretty insecure eventually his mother took him back in and wanted to

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make a farmer out of him but Isaac just wasn't cut out for the farming life and

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luckily for him and for us his teachers agreed with him they saw how crazy good

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he was at math and managed to send him off to college at Cambridge sure he had [Isaac standing outside of Cambridge University]

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to wait tables at the college in order to pay his way but that just shows that

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even super geniuses have to do work-study programs sometimes in 1665

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when Newton was still in college there was the Great Plague of London [People walking around London in the Great Plague]

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yike just the phrase Great Plague makes us want to go live in one of those

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plastic bubbles it's spread to Cambridge was so bad that they decided to close

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half the school for a year and a half you get excited for a snow day but a

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year and a half we might actually start to miss going to school consider our [Apple banging on closed sign at school]

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minds blown and Isaac must have missed it too

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because it was during this period that he started laying the groundwork for

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some of his most important work and while he's back on the farm working on [Isaac walking along wasteland farm]

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physics all by himself he was sitting under an apple tree when one of the

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apples fell and bonked him on the head and that's what inspired him to come up

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with his theory of gravity or at least that's the myth... in reality

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he just saw an Apple fall and that's what got him thinking, but the story isn't

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as good as the whole head bonking thing... embrace your legend I think embraces it

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sir Isaac's first major publication was all about optics and along with that

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book he invented the reflecting telescope remember when he said he was [Isaac Newton looking through telescope]

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super smart yeah we meant he was super smart but some people didn't like all

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these new ideas for example Robert Hooke old Bobby H here was a member of the

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Royal Society, the Royal Society is basically a bunch of scientists who get

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together and talk about science stuff for the benefit of science [Scientists at a table for the Royal Society]

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in addition science and science and more science but this club is pretty fancy

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pants and not everyone was happy about old farm boy here showing up and showing

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off Robert Hooke went after Newton pretty hard and Newton went right back

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at him for years they argued at the society and send each other nasty [Newton and Hooke arguing]

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letters just think of how epic their Twitter war would have been eventually

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newton won a decisive victory by outliving Hooke which is always a winning

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ploy but all this arguing wasn't worthless in fact one outcome of the

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bickering was Isaac Newton's philosophy a naturalis principia mathematica

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which is all mouth full of latin so let's just go with Principia... this [Apple discussing Principia]

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book was Newton's most famous work and it introduced his three laws of motion

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the Principia made Newton a full-on celebrity

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he became a member of parliament and president of the Royal Society in fact [Newton standing in Parliament]

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as president he ordered the destruction the only known oil painting of his old

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nemesis Robert Hooke yeah Newton could really carry a grudge... in this unit we're

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going to be diving deep into each of Newton's three laws but let's take a

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quick look at them now Newton's first law of motion says that an object at [First of Newton's laws appears]

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rest tends to stay at rest and an object in motion tends to stay in motion

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which sounds a lot like our Saturday mornings and our Saturday afternoons so [Boy laying on couch]

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basically this law says that all motion or lack thereof will be constant unless

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something changes it this is also referred to as the law of inertia

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inertia is a property of mass - mass is how much stuff is in a thing sorry if

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we're getting too technical here the inertial mass is a measure of an

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object's resistance to acceleration the more inertial mass an object has the [Apple trying to push a rock]

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harder that object is to move which is something that just makes intuitive

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sense after all you can make a ping-pong ball roll just by blowing on it if that

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same ball was made of solid lead well you can huff and puff until you pass out

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that ball would not be going anywhere and the game of table tennis would get [Man playing table tennis alone]

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much more dangerous this law also means that anytime motion changes it's due to

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a force acting on whatever is moving or not moving whichever the case may be

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basically if an object's motion changes some force is responsible for that

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change that force can be friction slowing us down when they put on clean [Girl skidding with socks on the floor]

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socks and do some sweet floor slides that force can be gravity after all

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without gravity bungee jumping would be like bungee floating or that force can

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come from our muscles like when we slink away from the table because old uncle

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Greg's talking politics again speaking of forces law numero dos is all about

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force it says that a force that's applied to an object is equal to the

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object's mass times its acceleration and that little arrows lets us know that

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force is a vector because every force is applied in some direction yes away from Uncle [Greg standing by burning barbecue]

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Greg counts as a direction we've looked at acceleration in a bunch of our

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previous exercises so we know that it's expressed in meters per second squared

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and the SI unit for mass is the kilogram so the unit of force is kilograms times

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meters over a second squared which doesn't exactly roll off the tongue so

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the bigwigs in charge of the whole SI unit system came up with a unit just for [Man standing in a library]

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force it's the Newton yep named after Sir Isaac himself like we

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said the Newton is made of kilograms and meters and seconds so if we're trying to

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determine a force at a t-shirt cannon exerts on a shirt that weighs 200 grams [Girl fires t-shirt cannon at a man]

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or the force that a snail exerts when it accelerates at a-blazing 3 inches per

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second squared we have to convert everything so that it's using the right

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units to match with the units that make up a Newton and of course what makes up

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a Newton is fig paste wrapped inside a delicious pastry dough come on

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you know we would make at least one fig newton joke

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the third law is one that you're probably familiar with already maybe

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your mom told it to you when you flicked your little brother's ear and he stomped [Boy flicks brothers ear and stomps on his foot]

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on your toe in retaliation every action has an equal and opposite reaction now

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this law might sound all deep and philosophical which it is when we're not

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talking about physics but guess what we're talking about physics to think of

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this law in a physics sense go blow up a balloon and use your own lungs not some [Apple blowing up a balloon]

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spare helium tank you have lying around the house now don't tie it off let it go

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see how it goes all over the place as the air escapes the balloon pushes the

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air out of it neck is that what you call that part of the balloon you know the

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air hole blow hole okay we'll stop there anyway the air is being pushed out [Air blowing out of the balloon]

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behind the balloon and in reaction to that action the balloon is being pushed

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forward okay let's look at some specific examples let's say Isaac wants to get

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away from plague town which yeah.. get out while you can buddy so he decides to go

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to Iceland why because in addition to being a genius he was born to figure [Isaac figureskating in Iceland]

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skate Iceland also pretty far away from oozing

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plague filled pustules he laces up his skates, finds a frozen lake and starts

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to do his warmups he quickly gets up to a velocity of 12 meters per second and

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he has a mass of 63 kilograms assuming that the ice is frictionless how much

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force is needed for him to maintain his velocity wait we have numbers here we

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know force equals mass times acceleration [Force formula appears]

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Didn't we promise that there wouldn't be any math yes we did and we're not going

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to break that promise right now what's the first law objects in motion tend to [Newton's first law appears]

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stay in motion and this is special pretend ice that is frictionless so it

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takes no force to keep Isaac at this velocity so the correct answer is zero [Isaac skating on the ice]

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Newton's other than the one in the wig doing the pirouette over there let's say

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that he's still cruising along skating his little heart out at 15 meters per

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second when he startled by a rogue seal he trips and falls onto a snowy patch

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where he slides for three seconds before coming to a stop how much force acts on [Isaac Newton upside down sliding in the ice]

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Ike to bring him to a stop okay so here's where we lied about not doing math

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whoops so what law are we dealing with here well we're trying to figure out the

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amount of force that caused Isaac's motion to change that sounds like a job

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for law number two force equals mass times acceleration we know his mass is

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63 kilograms do we know his acceleration nope but we can figure it out real quick [Apple standing on the ice]

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acceleration equals the change in velocity over time he started with a

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velocity of fifteen meters per second and his ending velocity was a big fat

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goose egg so the change in velocity is negative 15 meters per second and this

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slide took place over three seconds so the acceleration is negative five meters

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per second squared now we can plug that number into our force equation....63

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kilograms times negative five meters per second squared gives us a force of

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negative 315 Newtons since force is a vector quantity that [Newton upside down in the clouds]

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negative value tells us that the force was applied in the opposite direction of

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the initial velocity dust yourself off there Isaac we want to see a triple axle

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from you looks like that fall hasn't been a bad

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mood not that it takes much with this guy mm-hm

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let's say he throws a snowball at the seal nothing too hard that snowball just [Isaac throws snowball at a seal]

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has a force of 3 Newtons how much force does the seals head exert on the

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snowball we lied to you once we''re not gonna do it again

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there's no math needed here what's the third law every action blah blah blah

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something about a reaction right equal and opposite well the opposite of 3

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Newton's is negative 3 Newtons so the seals head exerted a force of negative 3

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Newton's on the snowball like we said we'll be getting up close and personal [Apple figureskating]

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with each of these laws this lesson is just making sure we're clear on the

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general concepts and we hope that you use Isaac as a role model for what a

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genius can achieve but maybe not for how a genius should act because when you're

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dealing with people you can't be sure they'll react to things predictably with

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an equal and opposite reaction people even seals might react in a way [Seal sliding on the ice]

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you weren't planning on like say when you hit them in the head with a snowball

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skate like the wind Isaac [Seal chasing Isaac on the ice]

Full Transcript