Physics 10 - Lecture 10: Electricity and Magnetism II

[gibin00795]

very very informative and useful......thanks to whoever made and uploaded it

[RIFF0RAFF]

I adore these lectures, but cameraman sucks big time.

[Falsate]

Physics or bust.

[immrbaldwin]

I would love to just sit and talk with this guy.

[coldshot5555]

I like it alot

[Eniacbc]

Thumbs up for the sleepy cameraman always screwing up

[saintpero]

I have a feeling the camerman is trying to sabotage this course!

[Redhouseab]

WOW SOMEONE FIRE THE CAMERAMAN. FFS!

[FateMaster2]

@Redhouseab Since the camera goes out of focus shortly after he activates the not schielded transformator my guess is, that that transformator's electro magnetic field is messing with the cameras auto focus.

[Redhouseab]

@FateMaster2 hmmm interesting idea. how would this field mess with the auto focus?

[FateMaster2]

@Redhouseab Well the transformator is used to produce a sparc and like Mr. Mueller sayed a spark generates an electro-magnetic wave. And that can inflict a lot of problems on electronic devices.

[Redhouseab]

north south north south south south north north north south

[JPO1618]

45:00 FOCUS!

[DerKiesch]

@why you are able to get faster than your fuel

Okay, first thing: There is no single inertial frame that can be seen as globally at rest - Meaning: You can always discribe your rocket in an inertial frame that moves at the same speed as the rocket - so in this system your acceleration from the fuel will NOT change depending on your momentary velocity. As long as there are no relativistic effects this will stay correct.

What Mueller is refering to is a different Problem (see next post).

[DerKiesch]

@DerKiesch

Rockets work on the principle of Momentum and Energy conservation. Okay, Energy is generated by the burning fuel, generating hot gases - so you need to know the chemical energy in the fuel. This is more or less given by the speed of your fuel going out of the rocket. Knowing this and the mass of the particles going out you can calculate your velocity gain. It turns out that this will increase steadiely (if the fuel burning rate stays constant). Why? Because you drop off mass.

[Animalvader1]

Just saw a typo: 1/2 speed of light is 150,000,000mps. oops.

[Casanova646]

I wish this guy would be my physics teacher.

[webdesignpr]

Excellent Class! But apparently wasn't good enough to keep the camera guy awake.

[DrGonzo39]

C-C-C-COMMENT!!!!!!!!!

[DrGonzo39]

Here's a comment.

[nasirmk]

52:30 holy crap coolest demo ever!

[joeglimmix]

@nasirmk i know! since it looks like a chinese wok, how cool would it be if he threw some veggies in and starting cooking them while it was floating in midair?

[nasirmk]

@joeglimmix now that my friend is an idea :D

[ki85]

Muller about rockets (vs. railguns; 57:00): "The fuel comes out in a certain velocity. Once you are going faster than its velocity and you are shooting fuel out backwards you are not getting all the energy out because the fuel is coming along with you. You are wasting energy." - I'm wondering if this is correct? The acceleration remains the same whether the rocket is faster or slower than the velocity of the fuel, doesn't it?

[recyclingismylife]

@ki85 the only thing pushing the rocket is the thrust, i.e. the force produced by the difference between the velocity of the rocket and the velocity of the fuel. i know it sounds weird, but if you think about it, it makes common sense. of course, the rocket will still move along without continuous thrust, and the air drag around it, or the gravity of the body from which it has been launched, will slow it down bit by bit. i hope this helps

[ki85]

@recyclingismylife Thanks for your answer. But I am not convinced yet. Can you be a bit more specific in terms of 'the force produced by the difference between the velocity of the rocket and the velocity of the fuel'? What kind of force is that? Has it something to do with pressure? I did some (short) research and its a while ago, but i think the acceleration comes from the repulsion of the air molecules or somethin... as if you sit in a cart and throwing a ball, the cart goes backwards...

[Animalvader1]

@ki85 I'll take a stab at it. In a vacuum (like space) you gain momentum by pushing off of the gas or fuel as it's expelled from the rocket. Once your forward momentum is = to the maximum expulsion velocity of the fuel from the back (probably from air pressure in your tanks), your forward momentum will not increase. With the rail gun, you can keep adding voltage to further increase velocity, thus your max speed is limited to your power supply

[ki85]

@Animalvader1 thanks for you answer. You say then that when I am sitting on a rocket at high velocity and I fire a gun I wont feel any recoil?

[Animalvader1]

@ki85 Rail gun is different than a hand gun. "Every action causes an equal and opposite reaction" The "recoil" of a rail gun is precisely what makes it a viable means of propulsion. Two static objects that are touching, are rapidly forced apart (pushing off each other) by an electromagnet will cause both objects to fly apart at equal speed in a vacuum. Gradually increasing the output of magnetism by adding more electricity will increase the speed of both objects

[ki85]

@Animalvader1 I am not talking about rail guns at all. I am just talking about rockets and normal hand guns. I am sure you are perfectly right but forget the magnetism for a second. I am not a physicist at all. My arguments base on pure intuition. My point is this: I assume the acceleration of a rocket is caused by some sort of 'recoil', similar to the recoil of a gun. Now why should there be no recoil, if the rocket (or the gun) moves extremely fast in the other direction?

[Animalvader1]

@ki85 Ok, this may take a few posts, bare with me: Think about this for a minute. You are driving an indestructible car down the highway at 50 MPH. You realize you missed a turn, and suddenly shift the car in reverse...What happens? Does the car A) instantly start going 50 MPH in the opposite direction, or B) screech to a halt and gradually start accelerating backwards until you reach 50MPH in the opposite direction? The answer is "B" because the cars forward momentum needs to be addressed first

[Animalvader1]

@ki85 (Continued) before it can have any momentum in the opposite direction. Keep this in mind while reading. While the bullet in the gun's chamber may appear motionless to you the shooter, it, the gun it's in, you and the rocket you are riding on, all have the same forward momentum while the rocket is moving. Lets say the rocket is moving at 1/2 the speed of light (150,000 meters per second) through space. That means the bullet is already moving at 150,000mps before it's even fired. In order to

[Animalvader1]

@ki85 (continued 2) have any momentum in the opposite direction, the bullet must first overcome it's forward momentum completely, otherwise it's just "slowing down". As soon as the gun is fired, the gun is moving away from the bullet at 150,000mps just because of it's own forward momentum. The force of the gun powder going off as the gun is fired is not enough to over come the bullets forward momentum and propel it backwards, instead you are just rapidly slowing the bullet down. This is the

[Animalvader1]

@ki85 (continued 3) waste of energy he is referring to in the video. Will the gun recoil because of the bullet "slow down"? I doubt it, but then, I'm not a physicist ether. I'm just a (clearly over-qualified) postman.

[ki85]

@Animalvader1 ...

[ki85]

@Animalvader1 Thanks for your explanations. I really appreciate. Two thoughts: 1. Where goes the energy you need for slowing down the bullet? IMO it accelerates the rocket/gun (what would result in a recoil - sorry if I am bullish. I just like to argue) 2. What about the 'Inertial frame of reference'? If you are sitting on a rocket moving with 150'000mps you can say: 'ok. I am at rest. Everybody else is moving with 150'000mps'. In terms of this 'law' it seems to me odd if there was no recoil.

[Animalvader1]

@ki85 Honestly, if this continues much longer, you're going to have to start paying me. All the energy goes into slowing the bullet, none is transferred to make the gun recoil because it is already moving in the opposite direction with more energy than the explosion of gun powder can produce (i.e. the rocket is already moving faster than the bullet could ever be fired, even from a stationary gun)

[ki85]

@Animalvader1 I'll pay you after you have convinced me;)... I think what you are saying is pretty surprising: There is no recoil of a gun if you move fast enough in space and shoot in the opposite direction. -What if you shoot in the same direction the rocket is flying? The gun SHOULD recoil cuz the bullet is accelerated. So: Depending on the direction I point my gun, there would be a recoil or not. Who believes that?! ps: bullet: 1000m/s; space shuttle 7860m/s - the exp. could be done easily...

[Animalvader1]

@ki85 Wrong. It's not my job to convince you of anything. If it were my job, than you can start paying me for my time. I've answered you initial questions out of generosity, but the rest of your education you are going to have to pay for. Read a book, take a class, call Muller......but I'm done. Good day sir.

[ki85]

@Animalvader1 OMG you are serious about that?! I never thought about that dialog as you educating me, sir. It was just a argument about a problem... If this is not fun for you, hey, dont waste one more second... thanks anyways and good day

[Animalvader1]

@ki85 Sorry if I sounded a bit harsh, but I never gave you the impression that I wanted to debate. You posted a question about something said in the video, I answered it. You wanted clarification, I gave it to you. If you are unhappy with my answers, you can look up the equations, plug in the numbers, and prove it one way or the other. Because it can be solved with math, there's little room for opinion, so why argue about it? We got our wires crossed, no harm done. See you around.

[r8qt7]

fine lectures but he seems to be some weird republican ...

[D0g63rt]

Is that some kind of strawman or are you just regular stupid?

[lelyn1234]

Why hasn't someone edited the video? Those "fails" are easily fixed!

[MrDurcon]

Fire the camera man for gods sakes.

[trovial]

very good lecture,

the guy filming this though, is the biggest retarded on the face of the earth

[TzerMaan]

To build the tower might requires large amount of money, but I am not sure how it function, do you mind explain it to me?

[Redhouseab]

Great lectures. Thanks for teaching us for free. :-) 5 starz

[guineapig1234]

Is this really called physics for future presidents? Thats pretty arrogant. Or humbling lol.

[lord1993]

great vid... camera man epic fails

[ispaniola]

Good thing the camera man didnt fail at 53:14

...HAHA :P

[NickRoman]

This is great, but wtf is up with the camera man?

[DjMajesticone]

This is awsome good!!!

Want more!

Knowledge makes u wiser u dumbs out there.. ;)

[Theninjagecko]

Attention... ATTEEEEEEEEEEEEENTION!

[Redhouseab]

hahaha. ::::Evil Stare:::

[megoku]

Ha - awesome finale! Great lectures.

[DoubleDutchBust]

After all just a test.

Dr.

[DoubleDutchBust]

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Physics 10 - Lecture 10: Electricity and Magnetism II

Horseraces 3:23

Electrictricity

[DoubleDutchBust]

Electricity and Magnetism II

QuantumHOOFigurescience

SesroHHorsesBelmont

QuantumHOOFigurescience

Electricity and Magnetism II

[w0083e5c]

if he's really woried about some shoe-bombs...what kind of explosive would you need to create a hole in an airplane when you only got a couple of grams.

one might notice that a hole in an airplane wont do much damage. nowadays it's just going to land.

weird to hear that from a physics teacher at a university. i guess panicmongering can effect anybody.

[laputahayom]

i remember watching air cash investigation where someone got on a plane with explosives AND a bottle of petrol/gasoline and stuck it under one of the seat (can't remember if it crashed though pretty sure it did) might be on Wikipedia

[w0083e5c]

he's talking about shoe stuff, not bottles. a bottle filled with C4 will create serious damage, of course. but you would have to wear shoes made of C4 to get that effect.

and i wonder why my previous post got a -3 rating. am i wrong? if so, feel free to correct me.

[laputahayom]

"and i wonder why my previous post got a -3 rating. am i wrong? if so, feel free to correct me. "

i think it because a lot of people think planes are VERY vulnerable to any sort of damage (not my view though).

[flyingporcupine2]

the reason the cameraman sucks is cause hes at least as baked as the proff

[lti12]

the camera man is a moron, can't even zoom in or focus the camera right

[themachinegunn]

but i think the cards actually work better when you put a peice of paper in front of the card before you slide it through...at least it seems to work better

[SlykeThePhoxenix]

The most exciting part is blurred =(.

[SlykeThePhoxenix]

Doesn't the library alarms use RFID chips mostly?

[havik1]

They use magnetic strips.

[MajorUtah]

Thank Youuuuu!!! For Posting this!! This is the reason we will survive as a species..

Hoorah... *XD

[SpankbankINC]

@MajorUtah This is the reason your mom will survive as a parent... I don't know what the point in that was.

[kingofdice66]

i think the emp(electromagnetic pulse) destroied the camera with that high voltage:-)

[Tippster1980]

Dr Muller needs a new Video Guy who can switch cameras better! =o/

[saluki5711]

we need videos on his nemesis theory!!

[tekproxy]

This guy simply does not lose his train of thought. It's impressive!

[Duracellabcd]

I'am an italian students in electronic enegineering , nothing is better than those videos to improve in english, and repeat\learn somthing ! thanks!

Congratulation for the lesson, this theoretical and praric method is very useful. much better than the thousands of calculus that make me do at my university X_D

[bamboo4tameshigiri]

<~~~ playing with my neodymium magnets while watching

[mszlmb]

Why do presidents need physics so much..?

[Julchen68]

Go and watch the radioactive part again :p

[mszlmb]

LOL ^_^

[brian1625]

Alternative fuels and resources, global warming, nuclear power, nuclear weapons or weapons technology, satellite technology, Spy Technology.

[Darkfoster22]

So you don't have presidents like bush =D

[eyehategod323]

this guy is a douche

[fellini141]

reallly great courses.I m a european physics student,thanks for this course,great teacher.

[ItzDiPzBaby]

cool way to end the class

[hanzakbar]

in the last lecture he promised he will touch on Electro magnetic induction.. he didn't :(

[brianfranch]

That's all I heard him talk about  O_o

the Transfomer... metal detector... that's all induction O_o

[ss4pg]

Nice way of teaching, you don't need to memorize crappy stuff from the book and study formulas. Understanding conception is what we need. I wish I have more instructors like Muller.

[lilbrudder32]

Finally someone who understands! Conceive with me!

[killersamuk]

this guy is great ;)

[LilRedDog]

There are no ceramic guns...

And you certainly cannot buy them online...

Very disappointed.

Calls into question everything else you have postulated..

[dwarfer777]

very poor teaching, professor

[killersamuk]

maybe for you, but its useful to the rest of us!

[alphadog7473]

I hope that means yes , I love physics

[alphadog7473]

stupid question but is it ok that those of us not enrolled in this coarse or any at all watch these ? if yes please post more , I assume so since its a public place but do you all mind ?

[mingooson]

I agree

[Rebirth960]

great video......

informative