Introduction to work and energy

[ahsenization]

Distance= S

Not D

[ps7556]

Thx so much!!! I have a physics midterm tomorrow!!!

[BoxParadox]

FAKE AND GAY

[humzaashraf321]

The future will be Khan Academy in every school

[Kricardose]

I am very happy to see the vidoe Introduction to work and energy after you give this

[bebeheuy]

I Love The Video Introduction to work and energy It Can Increase My Knowledge

[Mjhond]

Steady I Really Like This Video Introduction to work and energy

[MrPEDOCTOR]

this is great explanation. thanks

[pepsicokepepsi]

soo slooww snail academy

[RaffertyPK]

@pepsicokepepsi thats you know, its youtube, you can fast forward if you want....

[MrKoolBeanz2]

all this math doesnt make any sence at all!

[kutecurse6060]

@MrKoolBeanz2 sense

[Zizzerboy]

@MrKoolBeanz2 sense*

[lordkhalloody]

great jop  thx u alot now i know how the formula of kentik energy came

[capeenrage]

W=KE only works if you are starting (or finishing) at rest. This works well when your questions always start with no initial velocity. But for questions where vi or vf are not zero, W is more generally known as the Change in Energy, in this case Kinetic Energy. I'm certain the Khan Academy knows this, just want to make sure my students who are using these great videos also know. Thanks for the great resources.

[DarkApostleMatt]

I'm taking physics in highschool and I'm not very good at it...:(

these videos help a lot though :)

[poponinja1233]

Mr. foote

[jonrite]

I wish my student loans could allow me to send YOU my tuition money.

[badshabz1]

wikipeidia is sometimes wronng....

[hgdeviant]

my mind exploded at 8:01. thank you sir for your sneaky awesome explanations.

[alexander324324]

You are awesome dude! I was so desperate before i found your videos. Thank you very much.

[1999vandal]

I heard Khan is playing Conan the Barbarian in the new remake, only his sword is made of knowledge

[omgwtfbbq6666]

How to pass Engineering:

Change majors immediately before you get fucked in the ass. *check*

[Plonka4u]

Wow GREAT, a whole quarter year of physics work in fricken 9.18 minutes! Thanks Obama

[JaySmith91]

I like the part where he talks about work and energy

[zanzibarland1]

6:50 do you see anything that looks like work? 0.o

[SLHappyEmo1001]

@zanzibarland1 ya...it is te F*d inside the square root...

F*d equals work...lyk he says later in the vid...

[zanzibarland1]

@SLHappyEmo1001 yeah i got that, it was a play on words but thanks anyway

[RandomVortex]

Anything that promotes learning is wonderful!

[nickyyau1]

well i think that's not force x distance but force x displacement

anyway, that doesn't make much difference

[Jebrone]

IM LOST T_T man to many variables!

[QMANOULTON]

Thanks very much, this was really helpful!

[junior1984able]

you forgot to talk about power in joules, Sal

[doctorquantum]

@junior1984able well, if power was measured in Joules, it would be the right thing to do. But it's not.

[junior1984able]

@doctorquantum i gues you never studied juoules per coulumb, what a noob

[doctorquantum]

@junior1984able Power is measured in Watts. Energy is measured in Joules. One Watt is one Joule per second.  A Joule per Coulomb is a Volt. You're not dealing with a noob, junior.

[webhead615]

ohhh energy IS work!

[ifsofacto86]

HIS HAND WRITING BLOWS...

[aachikha123]

i had this feeling of great joy when i figured that the end equation for Work was the equation of kinetic energy. the aaaaahhhh music played in the back ground.

[crystalidx]

highschool textbooks have disgusting explainations

[hitmanvb47]

can you come to UNC Charlotte and replace Dr. Gerges? cuz that guys SUCKS!

[slowquik]

you make me hate my physics teacher more.

[slowquik]

you make me hate my physics teacher more.

[carlitos3o5]

If my physics teacher was as good as you, i wouldn't have to use youtube to learn!!! You're awesome and thanks.

[ballsoffury4]

C)No forces are doing work on the object

D)There are no vertical forces acting on the object.

Now if it is at a constant speed the net forces must equal zero and there is no acceleration. First off how does it move if something is pushing and pulling on it with the same force? Second, my book says there is work being done by pushing and going against (friction), how is there work being done if the net force is zero? Thanks and blessings :)

[kzhang1234]

@ballsoffury4

you don't need a constant force to keep something in motion-i could be wrong

[ballsoffury4]

Hi Khan or anyone who can help I'm very annoyed right now I seemed to understand Physics very well when I took the course but am having a little trouble as I am studying for the Mcat. Anyways I have this question

An object with a mass of 50 kg moves across a level surface with a constant speed of 15m/s. Kinetic friction=.7 which of the following is true.

A)The force exerted on the object by kinetic friction is negligible.

B) There must be some other horizontal force acting on the object.

[MrPMG1994]

@ballsoffury4 Yes, I think that if there is no friction or air resistance you don't need any force to keep something in horizontal motion, you do need a force to accelerate something: F = ma

[narutosramenbuddy]

YOU SIR ARE AN ANGEL. 

[Defqon10]

at 4:30, its hard to understand your ambiguous problem, doesn't really give me a good feel for how its quantified because then you bring out other kinematic equations which really confuse things.

[canucksrule1000]

MayahiiEDU is copying a lot of your videos

[Anthonyss4]

Thank you soooo soooo much. Seriously man thank you!

[thelastbattle19]

:D



[Joniel120]

Oh yeah, Are you a Physics teacher???

Because our Physics teacher was SO ANNOYING!!!!

[Joniel120]

@Joniel120 MR. SEGUIDO SUCKS!!!!!!!!

[deeeoss21]

this guys the man. makes it so much easier

[peterleeyu]

DUDE WIKI LIES

[misterman567]

very much liked the derivation of kinetic energy formula

[SmokerTJ]

its like getting taught physics by quagmire..giggity

[MaNeSh15]

@SmokerTJ how so?

[Guffington]

So, am I right and saying that energy doesn't actually "exist" in the same way that light and matter exist? It is just a model to help measure velocities and motion?

[meyouanushole]

@Guffington no energy does exist... in fact light is a part of the radiant energy spectrum we can see. To clarify, radiowaves, microwaves, infrared light, the visible light, UV rays, x-rays, and Gamma rays (nuclear blast strength radiation) are all the same thing...that is radiant energy.

[meyouanushole]

@Guffington It can't be a bit confusing especially since most energy is related to the motion of particles. Thermal energy is related the motion of atoms. However radiant energy doesn't relate to particles in that way. In fact, the Large Hadron Collider (LHC) collides atoms and destroys them, when you destroy atoms you release pure energy...there is no particle left. In fact, sometimes weird things happen and particles are created from energy (so "out of thin air" by the way we would see it)

[EscherVox]

I truly appreciate your videos and have used them quite often with my physics students. I work as a tutor / teacher and occasionally, no matter how well I explain something, it just has to be reinforced by another perspective. Great work and again, thank you for a valuable resource.

[ACeKANAy]

dude...wish i had a brain like u sal!!!!surely wuldve topped each exam!!1...thnx for ur vedios...it really helps!!!

[thatcutehughes]

To all the science teachers that don't want me to use my computer in class. I was watching videos on youtube posted by this guy because he teaches better

[eBiology]

A very well made video. Clear, decisive, supported by evidence (Wikipedia) and on topic. You could not ask for a better lecture.

[bhavoh]

Ohh I saw about this guy on CNN Student News...thanks a lot for what you're doing! It's really inspiring and you make wayy more sense than my science teacher :D

[crljohn94]

btw i would like to ask so is it true if i say (momentum x velocity= 2 x work)

this is derived frm my judgement in mind no 7:56..

[jewbinson]

@crljohn94 Yes. 1/2 (mass x (velocity squared)) = Kinetic energy = 1/2 (momentum x velocity)

[DBlack404]

well since u started at the beggining with the definitions i was able to clearly see the way the equuations got to how they are gotten and used.... thanks

[pieduk2]

Dude thanks to you i understand this much better now i cant focus with my science teacher unfortunatly

[ram79la]

thanks so much !! very detailed and clear

[yujisamadesu]

I think u are a physics phd holder dude....

[sharyleastlake]

Thanks, you are helping me become a better physical science teacher.

[jsherrill121]

It should be noted that energy is undefined. Although Mr. Sal used a highly conventional definition, energy can not be defined as an ability to do work; this is inaccurate because a system can have energy and still have no capacity to do work. Dr. Khan can post a video on this im sure; he is quite ingenius.

[ammarismat]

Tis guy is great

[Dundertaker]

Please continue making videos, even for old topics. I always look back at all your physics videos every month to just revise myself and every time it helps a lot more than it did the first time.

[dozza92]

thank you for that algebraic explenation to KE. Really helped :)

[ragsag211]

U MUST BE A PHYSICS TEACHER!

[plavch]

isnt Nm the unit of moment

[doctormurray91]

Newton meters describes work, as do ft lbs.

[bimboy08]

mannn ur going to help me alot im a senior taking physics and its confusing as hell

but sad part is you use radicals or w/e u call them when you do cos

[xofemaleraiderxo]

UR AWESOME

[Mizumi17]

I wish there I had some badass professors like this guy...... then maybe i'd show up to class everyday haha.

[maybeok1]

i am sooo ready for my exam!! thanks to you!

[1mj2288]

@maybeok1 And so am I! Ready to ace the exams. :D

[ColRon]

This is a great review for my physics exam. thanks a lot

[jnp4825]

this helps so much, thank you.

[sdegregorio]

Sal, is there a similar way to compute Work when initial velocity is not zero?

[Smooth258]

If I'm not mistaken, I'd probably say w=mv^2 / 2 - Vi^2 . :)

[calvinhobbesliker2]

I think it would be Vi^2/2 to get it equal to ForcexDistance.

[calvinhobbesliker2]

I was wrong. It actually is: W=(m/2)(Vf^2-Vi^2)

[HPPcello2]

thats KE isn't it?  work =Fd or W=Fcos(theta)s

[simsimsingh6]

yes it is! infact that connention helped me score pretty well on my physics paper!

[lesbmistique]

wow you have made physics soo much more bearable to me now.

[irfantea]

i'm a teacher, and i'm recently pointed to teach physic. i learn a lot from this video

[wanitshothot]

i like your video but I have problem in downloading it

[siaovast]

...i wish i found your videos earlier

[preciouskitten85]

thank you!

[idricool]

I like your videos and It is answering all my questions. Thank you.

[gunter84]

I just want to let you know that I am taking Physics 1111 at the University of Georgia and I find your videos not only informative but VERY entertaining. Thanks!