Physics is Fun: Why do objects fall? - PDF 무료 다운로드

Physics is Fun: Why do objects fall? Grzegorz Karwasz Didactics of Physics Division Nicolaus Copernicus University Toruń, Poland 송미영책임연구원 플라즈마기반기술연구팀 / 플라즈마기술연구센터 / 국가핵융합연구소

Toruń medioeval 중세도시 city (*1227) Established by German religious order 13 세기중반프로이센의정복과복음전도의기지로세워졌으며, 한자동맹의일원으로서상업의중심지로발달하였다토룬 ( 폴란드어 : Toruń, 독일어 : Thorn 토른 [*]) 은폴란드중부에위치해있는중공업도시이다. 1997 년에구시가지가세계유산에등록되었다.

Toruń city of cathedrals 성당의도시 Church S.S. John s Church S. Mary (Ascension to Heavens) Church S. James

Toruń Nicolaus Copernicus born 천문학자니콜라우스코페르니쿠스의고향 (1473) N. Copernicus (1473-1543) House of Copernicus father, rich merchant 부유한상인이었던코페르니쿠스의아버지 Lucas Watzenrode (Nicolaus uncle, Bishop) 코페르니쿠스의외삼촌, 루카스바첸로데

What happened in Poland/ Europe? 유럽 / 폴란드에발생한사건 Poland 1466: war between German order and Poland finished (peace in 독일게르만과폴란드사이의전쟁이끝남 Toruń) Europe 1453: Constantinopole (=Instabul) conquered by Turks 콘스탄티노플이터키에의해정복 (=end of Bizantine Imperium = 비잔틴제국의끝 )

Nicolaus Copernicus 니콜라우스코페르니쿠스 - 힘든학생 laborious student Kraków (1492-1496) S. Mary Church Bologna (1496-1500) Tower of Donkeys Padova (1501-1503) S. Antonio Basilica

Look into sky: Moon and planets 하늘로봐 : 달과행성움직여 are moving! Jupiter, Venus and Moon Bamberg, Germany, 25.03.2012 Trento, Italy, 26.03.

Ptolemeus (151-212): Sun and stars 프톨레마이오스 (151-212) : 태양과별이동 - 천동설 are moving Katedra Wniebowzięcia NMP w Toruniu

Nicolaus Copernicus: Earth is moving 니콜라우스코페르니쿠스 : 지구이동 - 지동설 He stopped Sun and Heavens, he moved Earth Terrae motor, solis caelique stator Copernicus Monument Toruń 토룬에있는코페르니쿠스기념비

Copernicus system: planets move around 코페르니쿠스체계 : 행성은태양주위를돈다 Sun Mercury: - 1 orbit in 90 days 수성이태양주위를한바퀴도는시간 : 90일 Venus: - 1 orbit in 9 months 금성이태양주위를한바퀴도는시간 : 9달 Mars: - 1 orbit in 2 years 화성이태양주위를한바퀴도는시간 : 2년 Jupiter: 1 obrbit in 11 years 목성이태양주위를한바퀴도는시간 : 11년 Saturn: 1 orbit in 30 years 토성이태양주위를한바퀴도는시간 : 30년

Copernicus system: everything 코페르니쿠스체계 : in movement Earth: - 1 rotatation in 24 hours 지구 : 1회자전-24시간 (=1 day) - 1 orbit in 365 days (=1 year) 태양주위를한바퀴도는시간 : 1년 Moon: - 1 orbit in 28 days ( 1 month) 지구주위를한바퀴도는시간 : 1달 - rotation in 28 days 1회자전을위해걸리는시간 :28일 Sun: - 1 rotation in 25 days 1회자전을위해걸리는시간 : 25일 Whole Solar systems flies 400 km/s towards Leon constellation

Why do all objects fall down on the floor? 왜모든물체는바닥으로떨어질까? Because there is gravity! 중력때문입니다! What is gravity? 중력은무엇인가요? It is Earth s attraction 지구가당기는힘입니다. What is Earth s attraction? It is gravity 지구가당기는힘이무엇인가요? 중력입니다 This is tautology: Rice is made of rice 쌀이쌀은만든다는표현과같이이는같은말의반복입니다.

Aristotle (384-322 BC) 아리스토텔레스 Objects fall, because they are heavy, and the natural place of heavy objects is the center of Earth 물체는무겁기때문에떨어지고무거운물체의본질적인장소는지구중심이다 So objects fall, in order to go to the center of Earth 그러므로지구중심으로가기위해모든물체는떨어진다 Let s try it! Let s try it again! Yes! Objects go to the center of Earth!

Can the ball jump up? 공은튀어오를수있습니까? And what about jumping up? http://dydaktyka.fizyka.umk.pl/nowa_strona/?q=node/314 Have a look And again... on this film! No! it was a trick. The film was inverted... 아니! 그것은속임수였다. 이영상은반전이있다 http://dydaktyka.fizyka.umk.pl/nowa_strona/?q=node/315

Can objects jump up? 물체는튀어오를수있나? Let s think all together: Jump up! (It is called tele-kinesis, and some people believe it) ( 그것은염력이라고하고, 어떤사람들은그것을믿는다.) It does not work. Is everybody really thinking jump up? 움직이않네요. 여러분모두튀어오르라고생각했나요? or somebody says: do not jump! Let s try it again! It does not work. The ball can not jump up!

I have a magic ball I will make a magic, and the ball will go up Magic, magic: go up! Now come back! Go up! Come back! Have you seen it? it s magic. Isn t it?

Now I will tell to this rubber ball, 나는지금부터고무공에대해이야기할것입니다. jump up to the roof! (Be careful) We learned it. Now we can jump all together! Why? We have energy!

This is energy which makes things move 물건을움직이는동력, 그것이에너지입니다 What do I feed these birds with? 내가새들에게무엇을주고있나? Balls? No! With energy! 공? 아니다에너지를주고있다 Why do these hens walk? 어떻게암탉이걸어갈수있나? Because I gave them energy 내가에너지를주었기때문입니다

We do work, to give energy This puppet goes down, because he got energy 인형이내려가는것은에너지를얻었기때문이다 This Santa Claus climbs, because I give him energy 산타인형이올라가는것은내가에너지를주었기때문이다

We work, to give energy Objects jump (and move, and fall) because they have energy 물체가튀어오르거나움직이거나떨어지는것은그들에에너지를가지고있기때문이다 This is another magic ball I will work on it (put energy) Now this ball will jump. Tell it: jump! This woodpecker will knock, if I rise him 내가딱따구리인형을올린다면인형은나무를두드릴것이다

How do objects fall? 어떻게물체는떨어지나? Now we know why do objects fall. 이제우리는왜물체가떨어지는지알았다. Let us ask, how do they fall. 우리서로에게물어보자, 물체는어떻게떨어질까? Do heavy objects fall quicker? 무거운물체가떠빨리떨어질까? Aristotle says: Yes! 아리스토텔레스라면그렇다고할것이다

Which cart is quicker? 어느쪽카트가빠른가? Who thinks that the heavier cart is quicker? Who thinks that the ligther cart is quicker? Let s try it! Which cart is heavier?

Which cart is quicker? We start with the lighter car The heavy should joint it. No! It did not work So try with the light one. It does not work either! The only explanation is that they descent with the same velocity! 유일한설명은동일한속도로하강한다는것입니다!

Galileo (1564-1642) 갈릴레오갈릴레이 All objects fall with the same velocity 모든물체는같은속도로떨어진다. Maybe he made objects fall from the Tower in Pisa 그는피사의탐에서물체를떨어뜨리는실험을했다 The Tower was leaning already in that time 당시에도탑은기울고있었다

Galileo Galilei: (1564-1642) 갈릴레오갈릴레이 What will happen if we make fall a heavy stone and a ligth 무거운돌과가벼운돌을동시에떨어뜨리면어떻게될까? stone? Heavier will fall quicker and light slower? 무거운돌이가벼운돌보다빠르게떨어질것이다.

Galileo Galilei: What will happen if we connect the heavy stone and a ligth stone? 무거운돌과가벼운돌은결합하여떨어뜨리면어떻게될까?? + = = Heavy and light fall together! 무거운돌과가벼운돌이같이떨어진다!!

Now, we try two balls: heavier and lighter ball? Shut your eyes! This is heavy, and this is light

Now, together: Listen Which carefully! was first? Open you eyes! They fall together! All objects fall with the same velocity!

Now, try it again Look carefully! The heavier is quicker! Why?

We try two pieces of paper One is ball, one is paper sheet This is the air which makes the difference!

Let s make experiment 공기없이실험해보자 without air There is no air on Moon, but we can t go to Moon 달에는공기가없다. 그래서우리는달에갈수없다 But we have a film 그러나우리는영화로볼수있다 This is a tube with a feather and a coin 여기동전과깃털이들어있는튜브가있다. We check what fall first 무엇이먼저떨어질까? coin or feather? Clear! coin is first!

Now we pump out air from tube 이제부터튜브로부터공기를빼도록하겠다 This is a pump, we wait untill air goes out And we try again! Now, coin and feather are together This is the air which makes the difference!

Now we make experiment on Moon 이제우리는달에서실험해보자 Apollo 17 (1971) This is an old experiment by Galileo 이것은갈릴레오에의한오래된실험이다 He said that all objects fall with the same velocity 그는모든물체는같은속도로떨어진다고말했다 This is a hammer and this is a feather 이것은헤머이고이것은깃털입니다. Let s try which falls first! 실험해봅시다 They fall together. Galileo was rigth! 이둘은같이떨어집니다, 갈릴레오가맞았습니다.

What is absence 중력이없다면? of gravity? Like in the space Eating in Space Station Gagarin, first man in space (12.04.1961)

We can make it here 우리는여기서해당상태를만들수있다 This is our space ship and pilot Will he jump out? No! he falls together The bear is in absence of gravity

We check it again Now water flows out No! water and the cup fall together! Water in the cup is in absence of gravity

But spaceship on orbit? 그러나궤도를도는우주선은? It goes around, not falling? 우주선은떨어지지않고궤도를돌고있다. Yes, it goes around but it is constant falling 그러나실제로는지속적으로떨어지는것이이다

How do objects fall? 어떻게물체는떨어지나? Now listen to this ball Close your eyes and listen How does the ball move? It goes with constant velocity

Listen again Now, it starts slowly and goes quicker and quicker The ball accelerates

Let s try a bigger inclined 각도가큰경사면 plane Listen to the film At what distance are balls? Equal, rigth? Now we look at the film

Let s measure 길이를측정해보자 distances Distances are 1 : 3 : 5 :7, i.e. successive 거리가 1:3:5:7 로연속적으로홀수 odd numbers This is the law discivered by Galile 이것은갈릴레오에의해발견된법칙이다

Successive odd numbers 연속홀수 s= ½ at 2 where a is the acceleration Science Center, Daejon

Laws of conservation 보존법칙 (1) Energy (kinetic and potential): E k =mv 2, m ismass, v - velocity E p =mgh, g is gravitational acceleration, h heigth E p E k Newton s craddle

Laws of conservation (2) Momentum (impetus) p = mv Experiment on recoil

Laws of conservation (3) Angular momentum L = m r x v celtic stone

Newton: Moon is constantly falling on Earth 뉴턴 : 달은항상지구에떨어진다 All objects (on Earth) fall g R=6374 km R=384 000 km g/4000 with the same acceleration g 모든물체는같은가속도 (g) 를가지고지표로떨어진다 Moon is more distant so it falls with g/4000 달은더멀리있어서 g/4000 가속도로떨어진다 (one orbit in 28 days)

Physics is Fun! But physics is also discovery: 물리학또한발견이다 Albert Einstein: ( 알버트아인슈타인 ) How can we recognize real absence of gravity from free falling? 우리는어떻게자유낙하에서중력의실제부재를인식할수있습니까? General theory of relativity 상대성의일반이론 (1915)