Centripetal Acceleration (part 2)

[raghavmc]

@khanacademy it has to be 30ft per sec per sec sir, no offense, I'm your die hard fan

[miniradman]

Does this take into account centripetal force?

[TooManyPBJs]

It's nice to have that intuition.

[pritamlaskar]

Shoudn't the unit of acceleration be feet multiplied by second inverse two, rather than feet per second?

[3888799]

i have a hw question where they gave me the

constat speed? is that the velocity

[smkdlian]

@3888799 nope

[sarah29172]

@3888799 thats the magnitude of the velocity.

[3888799]

i have a hw question where they gave me the c

onstat speed? is that the velocity

[joneparker]

Good Job, I like this. please reach me on Facebook, I love what you are doing here. Great job.

[joneparker]

Good Job, I like this. please reach me on Facebook, I love what you are doing here. Great job.

[rohman2]

Is there a lesson appling this teaching to when a whip snaps/cracks? I liken that situation to that of a person's spine going back to meet the top half of a seat back, not normally used in driving in this circumstance, it being rocked back to accomodate height, and the head snapping back and down finally to meet the head rest in a rear end collision. I am the person. I am trying to show that the ins. company engineer has neglected happenings inside the car when he calculated car impact force.

[narcomanel]

oh my god, I finally get this. It finally makes sense.

the teachers never explain stuff like this, and if they do, they spend 10 seconds on it, as if they remind it to someone that already know it. -_- d'oh

[ZahidAnwar5555]

Is the acceleration is uniform in uniform circular motion ? plz sir ans me

[ZahidAnwar5555]

Sir why we take V2 .....plz give me ans in written form I must need it.....our physics sir can not explain it ...

[Ann0y1ngFaN]

Í've got more intuition now

[Ihatenicknames1]

Why are we always in deep space, and not a nice place like Bahamas :/ 

[LucyGoozie]

Thank you so much. You are a physics angel! :)

[aachikha123]

i keep getting mixed up between acceleration velocityand speed=[ can anyone explain please

[Ihatenicknames1]

@aachikha123

Hi there :) The word "velocity" means someone is moving at the same speed all the time. For an instance, if you have a velocity of 1 m per seccond, you are moving 1 meter every seccond, the next seccond you will have moved 1 meter more, and in the seccond after that one more. You will not hurry up or slow down, but always walk at the same speed.



[Ihatenicknames1]

@aachikha123 If you accelerate though, it simply means that suddenly you changed your velocity. So if you accelerate you suddenly start moving faster or moving slower then you did before. You are only accelerating in that one moment when your velocity changes. So you could go from walking 1 meter per seccond, to suddenly walking 2 metres per seccond, in the one moment when you change the velocity you are accelerating.

[Ihatenicknames1]

@aachikha123 I know this can all be very confusing x) I struggled with it myself, just keep thinking about it!

[MitchBodmer]

Nice try, JOHN MAYER.

[ericmohr6]

Excellent videos. I'm a student in college and this is saving my life. You are extremely good at explaining these concepts and I am very grateful. The Khan Academy is saving my college education lol

[WOWFPS]

how do you know when to use either v or a for the speed?

[edmundstoiberderdepp]

@WOWFPS

v is actually speed (velocity, m/s), a stands for acceleration (m/s²)

[Xclann]

So cartoons are actually pretty accurate! When you run very very very very very fast... you actually start flying! XD

[neo92vip]

For F***S sake... nice video but seriously start using SI units ie. meters not feet...

please

[ichbinhornig10]

2 people have been hit by someone swinging a rock around

seriously thought these vids are awesome :D

[90vya]

thx!!! great vide0..

[Coombesy2185]

a great little study tool, good work mate

[100nassar]

SalFirst: GREAT WORK! (concerning physics:Centripetal Acceleration--Part 2) It is INCORRECT that a sub c is inversly prop. to r. You need to look at (w^2)r for this--not (v^2)/r...and keep in mind that v if a fun. of r.

Thanks,

--dale

[jonnygrossman]

Sal, as bomberfun1 noted, in your orbiting rocket example, the acceleration is 30ft/sec (instead of ft/sec^2). I would put a balloon comment on this error because your previous video did a great job of distinguishing xy velocity vectors and xy acceleration vectors and students might get re-confused on that distinction, if you don't.

[adamsx01x]

where can i find the video about gravity which he talks about ?

[BogMonkey53]

The SI unit for acceleration is m/s^2 though. Why would you use inches?

[bomberfun1]

@ BogMonkey53:

You have to know how to use inches to meters and back in order to rock any exam. The reason why I said it is because @ 08:10 the author uses acceleration (30 ft/sec) but seconds aren't squared, whereas they should be!

Food for thought for those who did not notice that.

[BogMonkey53]

In Ireland the road signs are in miles and the butchers sell meat by the pound but things are measured in cm rather than inches.

[adamsx01x]

@BogMonkey53 becoz stupid americans are still using imperial measuremenrs!

[BogMonkey53]

I just looked it up and found out USA is the only country that hasn't adopted the metric system. Jesus christ they should just make the conversion and get it over with.

[UberCuba]

@BogMonkey53

its annoying that they call the imperial system, the english system, since england has adopted the metric system ( far superior since water is the best!)

[EvilFatCat]

@BogMonkey53 Actually a few countries in Africa use the same measurement system as the US too.. Haha but yeah I agree that all should change to the metric system.

[BButterz88]

dude...........YOUR AWESOME!!!

You really know how to make things very CLEAR!!!

I'm loving physics even more now!

<3

[MichaelisOnYourtube]

this heeelps!

sal's the man!!

[WannaBeiDev]

To the comment below me are you being serious or funny? -.-

[pbrskater26]

This is really awsome but my math is tarrible! Ok, my brain synopsis cant prosess math or spelling as easy as other people, I got a learning dissibility, it dose not mean I cant understand it just takes longer for me to understand.

[killa34334]

To pbrskater26

Me too, I would say i have a learning dissibility but it takes me long time to understand a simple calculation/ or i

have 2 practice a few time to get the idea

[woo216]

thanks sal your great your videos are better than any teacher explaination i reckon you should have be a physics teacher

[stevogriff12]

intuition

[polos505]

this is very clear. nice job. I'm getting smarter after every video.

[woodenjaw]

I concur! :)

[letsgobuffalo9]

wow these video's are amazing

[healthyforyou]

Nice video, very helpful, but you said acceleration was in ft/s, shouldn't it be in ft/s^2?

[xsajienx]

Yeah. The units for acceleration would be ft/s^2. But still...amazing videos. They have been helping me understand my physics classes much better. Khan is an amazing person.

[polos505]

sorry i accidentally Thumped down your comment. anyway, you are correcct acceleration should be ft/s*s. I think he forgot to put the square there. nevertheless the video was very understanable.

[blinkbdj]

@healthyforyou he's made this mistake in a few videos. give him a break though, he's a good teacher

[healthyforyou]

@blinkbdj I know. But I'm sure many people were wondering about this. So I commented so that they would know that there's an error, that's all.

[mumbowumbo]

@healthyforyou He is not working in standard units either, velocity should be in ms^-1 and the radius in metres etc.. (ms^-1)^2 / m = ms^-2 m^-1 ..?

Sorry if I am wrong anywhere :) ..?

[bloodjunkiepr18]

thank you so much. I fell more confident to take my test now!

[volintine]

yeh he makes awesome vid not confusin at all

[dalaiwtf]

awesome^^

[zguitarmaster]

Very good explanations. Not confusing at all.

Keep your faith and keep educating. You might not get a million views but your really helping a lot of people that care.

[anava84]

hmmm I thought you gave us velocity as 30 ft/sec?

[ReaverKS]

It made complete sense, 5 stars

[dandanish]

thanks