Conservation of Energy

[Kricardose]

I am very happy to see the vidoe Using the law of conservation of energy to see how potential energy is converted into kinetic energy after you give this

[bebeheuy]

I Love The Video Using the law of conservation of energy to see how potential energy is converted into kinetic energy It Can Increase My Knowledge

[Mjhond]

Steady I Really Like This Video Using the law of conservation of energy to see how potential energy is converted into kinetic energy

[MrPEDOCTOR]

worth watching,. I learn a lot from these channel.

[MrKoolBeanz2]

great job mr khan, you saved the day again!

[bladervinay]

Great video as always from Mr Khan well explained

[adamaqmal]

God Bless uploader.

[WinnieTheDonut]

Thanks, man! God bless you!

[diznikkatuan]

thank you so much! I realize that i learn more from your educational videos than what i paid to learn in class! I learn a lot from your videos for my Chemistry and Physics! Great help. Please keep up your work.

[NationalPro]

FASCINATING!

[JazzoFett]

THAT MARK AT 4:50 BOTTOM LEFT IS KILLING ME.

[MetalSio]

I think my physics teacher saw your video because he did the same example. The only difference is that he couldn't do shit on the board!

[monahal1]

he is a BEAST! i Love him!!

[niconikko]

This was the first time I saw teacher khan used a rectangle to draw a box....

In the other videos, he preferred drawing by pencil

[MrAlienpirate]

the box is moving so fast it colour changes due to doppler effect

[tafi2faby]

I HATE MY TEACHER !!!

HE IS SOOO FUCKIN STUPID:@@

[The3nlightened0ne]

I've never seen anything as beautiful as mathematics

[NoahAndABadger]

what if it's through up into the air at u m/s and at 5m high KE=2.1, how do you find out the initial velocity?

[h5348227]

your a life saver may allah give you a long life full of happines

[ninjaturtle205]

when the object slides completely 10 metres why does it have a horizontal velocity? the object clearly moves under the sole influence of gravity which is vertical.

[voutasaurus]

@ninjaturtle205: Good Question.

There is a force being applied to the box by the surface, because otherwise the box would fall straight through it. This is the "normal force" which is talked about earlier in the playlist. So the force accelerates the box, thus changing its velocity, but the work done by the surface is assumed to be negligible, so the kinetic energy doesn't change, which means that the velocity changes in direction only, but I'm not entirely sure why it's negligible.

[NewEnergySavingTips]

save a lot of energy with universal eco urinal......here on you tube.....

[TheRidas11]

I am thankful for your videos! I wish you were my teacher! very great explained :)

[legojadlgj]

SO HELPFUL.

[MistaBlank79]

4 people dislike changing box colors

[wc1hater]

Wait, doesn't that only work with straight routes? If it's curvy, then energy must be lost while going up against the the first slope...I'm not sure if the speed would be entirely accurate, even in a vacuum in a frictionless environment... gravity still exists, right?

I mean, try to take the speed at a height of 7 meters... I'm pretty sure it won't be right. Am I right? Sorry, I haven't even taken physics, yet, so I don't know about this stuff...

[soapinmouth]

HOLY SHIT THANK YOU PLEASE COME TO CAL POLY POMONA

[greekcuty66]

i so wish this guy was my teacher..

[quidproquo2004]

Good explanation, but I would advise against using double standard characters as symbols. Rather than using PE for potential energy, I would use E subscript P. This way, there is no ambiguity.

This is what I do with my students.

[perlaabad]

tnx... ur amazing!! wheres the next part? pls tel me...

[kzhang1234]

@perlaabad

all of the videos are in order in the physics playlist just to let you know

[FallofDarkness55]

the conservation of energy proves that god exists.

[smarttieful]

My physics final tomorrow is about this. Thank you so much for explaining it!

[bisharalol]

"I WILL SEE YOU IN THE NEXT VIDEO"

*you never actually see us :( *



[willmer3]

did anyone get really frustrated when he didnt erease the little dot in the left corner?

[Goodfellow7]

@willmer3 The way he repeats himself a million times is equally frustrating.

[0dontspeak]

His voice is soothing. And he's GREAT at teaching! I understood it so well.

[AzyrenIshida]

With nuclear physics, you can just constantly take apart and put atoms together as much as you want because that CREATES energy

[bisharalol]

@AzyrenIshida noway

[jiggaluv123]

You explain everything so perfectly. You tackle the core principles so well, I think that's why you are extremely successful. That's why you are the best. One can't run until one can learn how to walk. Excellent work!

[NeoXC]

Wow, the part where you say the box falls at 10m/s at a height of 5 is mind blowing.

[OntologicalQuandary]

Can someone explain why this works for the slope of the ice? Wouldn't the acceleration be different than g since it is falling down an inclined plane? Shouldn't the potential energy take into account the upward and horizontal movement of the object? Because if the potential energy is the energy required to do move the box to that starting location, it would require vertical and horizontal force, not just vertical

[ubercute1sf]

@OntologicalQuandary I thought that too but just think about an object that goes down a hill then back up it speeds up going down and slower coming up but as it is coming up the KE gets less and PE gets more because of the height. Draw these two situations a bunch of hills and a ramp and another ramp at a different angle and you can qualitativally see this.

[AnImoL2]

the KE being 100J... ok attrition 0, but wtf then the box is glued to the ice what is that a bullet train(ok it's easier to show if it is glued to the surface)

[opmike343]

I swear, ALL college professors should be required to watch Khanacademy and PatrickJMT's videos before every stepping foot into a classroom. Too many of those guys (while VERY intelligent) have forgotten, or never learned, how to "teach".

[kardona91]

sneaky calculator at 3:40

[kabur88]

I thought that mass is in Newtons not kg and weight is in kg

[pyLz]

Nice video, but I wonder to what extent the conservation of momentum is affecting your result (the slope is being pushed to the left).

[Moby93]

You rock my wolrd!

[DevineProducts]

You dazzle my world.

[TuningAnApple]

For you problem with the box being dropped on the crazy slope, since velocity is a vector, wouldn't it's direction affect PE and KE? It's direction seems to be changing constantly too. So, do we just ignore direction?

[jewbinson]

@TuningAnApple Yes. Energy is a scalar, not a vector.

[PeaceFighter2]

Can you solve for me this problem?Or someone else...

When a 4 kg ball is thrown upwards at 40m/s,at what height is the PE equal to KE?

[TuningAnApple]

@PeaceFighter2

I might be wrong, but calculate when the ball is at the peak of its trajectory (where the velocity is 0), and at that point find the distance of the peak from the ground (or bottom of cliff, where ever it's landing). With that you can calculate gravitational pot. energy. Then you can set initial potential energy + Kinetic energy equal to final potential + Kinetic energy and solve. At that point of energy you can use Energy = work = force x d and find distance. Force being mg.

[3Rton]

@PeaceFighter2

Since it asks when is potential energy same as kinematic energy you can form formula:

1/2mv^2=mgh now since we know the velocity upwards and mass we can solve h which is the height in which the energies are same.

1/2*4kg*40m/s^2=4kg*9.81m/s^2*­h

Since both sides have mass we can simply take it off leaving the calculation in form-> 1/2*40m/s^2=9.81m/s^2*h now to get h we will just divide the whole calculation with 9.81m/s^2 Damn out of space.

[3Rton]

@3Rton I am not totally sure if this is correct but supposing that we want to know when the energies are exactly same it should work right?

[coolguy6075]

At wich period of education do you guys from the states learn this stuff??

[conve4521]

your a wonderful man. god bless your parents for creating you.

[thebigdille]

so much more understandable now

[nomania]

I LOVE YOU KHAN SAHEB. GOD BLESS YOU.

[Skies678]

thanks for these videos, I read my text books frustrated with confusion, come on youtube, watch the related video on your channel, and leave with a complete understanding of the concept!

[RADHE143]

What will be PE of a body kept on ground?

i mean h=0 then PE should be zero

and also at rest 'v = velocity' will be zero than where is the kinetic energy

[sharikokaine176]

@RADHE143 Well actually, even when you are on ground, you have gravitational potential energy. What is gravity? it's the force that pulls you towatds the centre of the earth, but you're not really AT the centre of the earth when you're on ground, u're actually a long way from it. But i guess we assume P.E. = 0 @ ground to make it less complicated.

[sharikokaine176]

@RADHE143

[Migelangel30]

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[Migelangel30]

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[TheWishification]

I LOVE this man..

[palestineftw]

@TheWishification no homo

[silent07killer]

oh i love this guy...this guy makes phyics easier for me no than my teacher in school....

tnx so much...

[chrisofnottingham]

Another way to state the consequence of this approach is; whatever the shape of the path which the object takes on its journey, its speed at any particular height is always the same. It's a shame that friction messes things up but in the world idealised ice slopes and perfect roller coasters I think its a really fascinating outcome.

[stealinglemons]

7:27 haha got my head back into it.

[bradkey98765]

It also changes colour when it falls :D

[saharmina]

@bradkey98765

hehehe, I lol'd when he said that

[mohtaprashant]

@bradkey98765 LOL

[mohtaprashant]

@bradkey98765 also the shape :D

[stepneyfan]

thank you so much!! I have a motion test tommorow, and now, thanx to you, i finally understand!!!

[rampriyadarshini]

awesome

[aeropostale]

oh snap. that makes sense.

[deathbystarship]

you missed a spot when you were cleaning lol

[Whatsthedealwithit]

your videos are amazing our physics teacher isnt the greatest but she tries .. she admits your videos are better and uses them all the time to help us understand concepts thanks for sharing your knowledge

[television758]

Wow! Thanks so much for sharing your awesome knowledge. You really are an amazing teacher!

[rm130]

you make my life so much easier!

[jrBunny1979]

These videos are very good.

Thanks for posting this.

[1055555grace]

the law of the conservation of energy!

[gklrajan]

hmm.. at 3.54, u said the unit of elocity as m/s2...

but neways gr8 wrk! thanku!

[scyllis]

NO, he meant V squared...

[soccerfanatic11]

thnx sooooo much, everytime i dont get something, u just make it sound so much easier... lifesaver

[SQUEEZYPOP]

Okay, You know what you're talking about... If energy "Cannot be created or destroyed" where does your energy go after you die?

HUH...

[Paulorific]

Energy can't be created or destroyed but it CAN change from one form to another. Our "energy" is given off as heat anyway.

[benjoandrichie]

um i think you need medical help imediatly

[beebop46n2]

Microorganisms involved in breaking down your proteins and other forms of potential energy from organic molecules.

[Ren520]

decomposers break down ur thang and the nutrients get reused by some other organisms

[mohtaprashant]

@SQUEEZYPOP the organisms who eat or decompose u take it , or if u are burnt then it gets converted into thermal energy , or if you went in space to commit a suicide then it will be your little parts' potential energy :P :P :P :P :P :P

[noimaginationnowings]

heeeeey, how did you do that?

which program did you use?

i need to make a video about the conservation of energy. D:

[laputahayom]

he used a screen recorder and MSpaint (and a mic).

[mohtaprashant]

@noimaginationnowings paint :P

[polos505]

sal,u r the man.u have taugh me a lot.thank u.

[ToastFroEva]

THANK. YOU.

[honeypot11]

i just wanted to say thank-you for putting the time to make these videos for us. I think that you sound better than my physics teacher! lol and i laugh a bit at the little jokes you do xD and the shaky mouse sometimes (yes im weird) thanks again!

[monaegr]

lol honeypot

[i3loodhunte31181]

So good at explaining! Thanks Sal!

[mariahkraft]

you sound hot. Also, I think i might actually understand this stuff a little (ok, ok a lot) better

[armyrule0111]

thanks..easy to understand.

[drorharush]

Thank you.

[idricool]

You are very smart. I hope all lot of people learn from this video. I am in grade 10, doing physics 11 and I am trying to learn energy before the teacher gets to explain it. THANK YOU !!!!!