Average velocity for constant acceleration | One-dimensional motion | Physics | Khan Academy

[@paulschlacter2182]

You've helped me more than my teacher could. Thank you, keep up the videos. Your lessons are easy to understand and you explain in such a better way than me teachers

[@navjotsingh7360]

don't you think he is one too

[@elviszhang2853]

Khan is my savior

[@baphnie]

My secular thoughts exactly!

[@seandimmock5813]

Hail khan

[@comrat9805]

truth

[@taylorg1113]

Jesus*

[@babatunde3775]

@@taylorg1113 not everyone is christian fam

[@thedogdogification]

I've never had a teacher systematically break it all down this way and show just how "common sense" the equations are. You don't take shortcuts, you just patiently go through the whole process so we can see how everything fits together step by step.

[@mubarkas8876]

I could never find acceleration an easy topic in physics. Now that you explain it, it makes so much more sense. Thank you for taking your time to make this video

[@megashani91]

actually it helps when he colour codes because it helps to see where a variable goes after each step

[@IBeExtraCool]

I'm 25 years old freshening up on some physics for my university physics 2 class. I was spacing off until I realized you were writing down a much easier way to get 1 of the kinematic equations. I would trade for my Russian teacher ANY day especially since I can actually understand you too lol.

[@ItHappens117]

sweet, sal. I actually understand now, as opposed to the vague 'uh huhs' i used to mutter in class. Thanks!

[@jobairahmad742]

you are blessings of today students

[@LynzeeLove]

I know this is an old video, but I'm not even lying when I say it took you FOUR minutes and it clicked for me when I've been struggling so hard 😢 my professor seems the type that he expects us to already know this and I've been struggling the past 3 weeks. Thank you so much!

[@maaaaddieee]

I have never been taught that distance traveled is the area under the velocity vs time curve! That is just awesome. You are really good at explaining why these equations actually make common sense! Thank you for that! It's really helpful!

[@ambers123100]

Mr.khan, you are is man of awesomeness

[@davisjohn-d6h]

Thanks Sal! Great video, I learned a lot!

[@scottnorman1940]

This I amazing, that fact that he breaks down the equation to fully understand why everything is in the equation is amazing and easy to understand.

[@Hino_55]

Ah i get it. Area of rectangle + Area of Triangle = Area of Trapezium Area of trapezium is: s = 1/2 * t (u + v) where 1/2 * (u + v) is the average velocity. I see. Its all connected, it's just a matter of being aware of the different perspectives you can use to view things. Credits to Sir Mahesh Shenoy of Khan Academy India English for his excellent derivation of the 3 Kinematics equations under his Class 9 CBSE Motion Playlist. Thankyou Sir Sal & Sir Mahesh!!!

[@DK-nz6bp]

Thnx... Khan academy.....

[@bestbrothersra6205]

Thank you very much sir. This vedio explanation helped me alot in a calculation. Once again thanks sir.

[@rizokhon5677]

You explain everything in such a clear way that you make it so easy to follow and understand. Now I'm understanding where formulas come from

[@stevestadler4634]

This just blew my mind. No one had explained it this way

[@averygee794]

Why can't teachers explain it this way?!!!

[@iMusikkForeva]

he's so amazing!!

[@JohnDoe-ze8pf]

I know right?! This guy is amazing.

[@sushicartman01]

Thanks man, you're sooooo helpful!!

[@sandeepsinghnegi2012]

That's awesome explanation...ever

[@thomasgaertig9453]

so much better than crash course physics, thank you for teaching for intuitive understanding

[@fleshcookie]

Who needs those silly kinematic equations are professors throw at us? YOU THE MAN SAL!!!!

[@thinginground5179]

At the start of this lesson I would have looked at this and seen a bunch of jumbled figures that my mind can't comprehend... At the end I can actually understand physics for the first time in my life!

[@magicman198765432]

And also his formula for calculating Vf is the same as Y=mx+c. You have a constant and you have the constant velocity that is dependent on seconds

[@ciao_abhi]

Mr Khan, did you notice that the final distance formula is just a formula to find the area of the trapezoid shaped graph? A= 1/2 (b1 + b2) h ? Thus u just proved how the area of a trapezoid is the combination of a triangle and the area of a rectangle. And interestingly enough the average velocity, which u termed 1/2(Vi + Vf), times the Δt is EQUAL to the total distance or the area of the trapezoid which IS the area under the curve. WOW VERY INTUITIVE lesson and unforgettable the way u teach..

[@pokeanalysis4917]

just wanted to say that the formula is very intuitive and thanks to you I now understood where v = u + at came from

[@philliptubego3946]

Topics are good

[@davidbondy2250]

I can't be the only math student who was yelling "INTEGRATE" when Sal Khan was talking about finding the area underneath the line on a graph.

[@messianichebrewshawnkawcak1550]

David Bondy he was trying to avoid the Calculus part for the moment I am sure .

[@AchiragChiragg]

your're correct if the initial velocity was 0 m/s but since initial velocity (Vi) is 5 m/s u have to subtract initial from final velocity S=(Vf - Vi) X T , hope it helped.

[@wyskun]

I have a very important 2 questions for me:) 1. In space, there is a space shuttle that does't move. Mass of this shuttle is always constant. This space shuttle has a rocket engine which produce a constant force of 100N. When the engine is started and the ship has a constant thrust of 100N, when the ship starts to accelerate, will the acceleration be constant and remain constant (let's assume 10m / s), or maybe the acceleration will start to decrease as the speed increases? It is related to the rule Ek = 1 / 2mv ^ 2 ??? 2. Same space shuttle doesnt move. Shuttle start to accelerate from 0km/h to 10km/h in 5 seconds and it takes "X" energy for example. How much energy it will needed to accelerate also 10km/h more in also in 5 seconds when it allready have velocity of 100km/h ? Also "X" energy? Or much more "X" of energy? And why is that?

[@gad416502]

Sir video was very easy to understand, on which app did u recorded it, I'm curious ?

[@raynedeerman]

ur right, especially since in the US you take physics 2 years after you take geometry. and if you are taking a calculus based physics class, you already have enough to recall from calculus while trying to take on all of this new information :P

[@Michael-cc4qf]

the formula at the end for distance is the same as the formula for the area of a trapezoid, with t=h and b1=vi, b2=vf, and Displacement/distance=Area. Which makes sense: the shape you see is also a trapezoid.

[@CrazyShooter199]

I already know everything from episode one to this episode, but I still watch it because... well I don't even know, because sal is awesome I guess.

[@MRFARMS2]

This makes sense cause integral of V is X(position)!

[@Peter_1986]

It would be rather ignorant and haughty to randomly use formulas that aren't super-familiar for the general public. The beauty of Salman Khan and his lessons is that he always makes sure that anybody, no matter how little previous experience, can understand what he is saying.

[@bernardlz]

Crystal Clear!

[@jcen123]

What is the air speed velocity of an unladen swallow?- Just had to ask.

[@uunz4435]

What do you mean? African or European swallow?

[@nuzhatmirza9467]

I hope that is what you want

[@guanatail]

I got a bit confused, around 7:00-8:00. you said the base is 5 then base change to 4? how's that?

[@skeir4317]

This is amazing

[@lokmanhossainlokman6422]

Is it distance or, displacement 12:12

[@SomeRandomFellow]

another way to get the same formula is to take the resulting shape, and realize that it's a trapezoid, with bases vi and vf and height Dt. using the formula for the area of a trapezoid, you get the same formula

[@deepeshrastogi]

Some Random Fellow yes....I do it that way too...

[@drevil37373]

anyone else thin of sequenc and series here,. you take the initial velocity plus the final velocity divide by 2 you get the Average and or mean of the velocity. multiple by the number of velocities you get the total distance traveled. Just like in Arithmetic Sequences you take the first term plus the last term divide by 2 you get the average of the sequence multiply by the number of terms you have in the sequence you get the sum of the sequence.

[@abdulbarihussain2813]

To find final velocity why are we multiplying acceleration with Delta time. Can u explain ?

[@1ntelligentDiscourse]

This is a first-year physics topic. The first year of physics is generally algebra-based. Integration is a calculus topic that wouldn't apply.

[@Songohanssj2100]

I am sorry but why displacement came out to be 36 m? If we apply the formula S = V X T as Vf=13 m/s and T=4s so S = 13 X 4 = 52m. where did I got it wrong? please help me

[@nuzhatmirza9467]

Can anyone please tell me that for which class is this video, please.......

[@AlphaTesting]

Beautiful.

[@shakinjunt]

dam I have been stuck on a hmwrk prob for like two hours I think things are starting to get cleared up. why the hell could my teacher just say what this guy did in like 15 min

[@blueunicorngreencupcake6477]

You should be our physics professor😂

[@hellojennification]

OMG! You are the shit! I am so blown away by your teaching. thank you much!

[@rrezonbeqiri5059]

How can i solve for time with this formula

[@Hermon17yr]

Va=(Vf+Vi)/2 is right but in this video u said Vf=Vi+(t)(a) I totally confuse where is 2 at in this derived formula

[@songerated2831]

why is it 1/2?

[@nuzhatmirza9467]

FROM THE WEB The sum of the initial and final velocity is divided by 2 to find the average. The average velocity calculator uses the formula that shows the average velocity (v) equals the sum of the final velocity (v) and the initial velocity (u), divided by 2. This is from the web👆

[@78anurag]

It's 1/2 because he derived the formula by adding the two areas (Rectangle and Triangle) watch the derivation again

[@thinginground5179]

@@nuzhatmirza9467 Or a clearer answer, without the added garbeldygook, would be that the area beneath the slope was half of the entire area between the Final Time and the Final Velocity.

[@samus1225]

so THATs why the 1/2 is in the formula :)

[@dageron97]

Shut Up and take my Physics Teacher!

[@Dark4Sant26]

6. ) A row boat, starting from rest takes 11 seconds to travel 34 meters. If the boat maintains a uniform acceleration, what will be its instantaneous velocity at the end of the 11-second period?? 17.) At the point in the stream where the boat is crossing, the stream is 202 meters wide. If the boat in Question 16 maintains its final velocity for the remainder of the trip, how much time will it need to reach the opposite Shore? 18.) What acceleration did the row boat initially experience in Question 16?? So this is a Question of my Teacher Wherein i want to prove that I made the right answer. Can you please solve this ?? Because I am having difficulty in proving something without concrete evidence from other Physics geeks.... I know this is a really easy problem but I need a more concrete proof. I have already done this but I am trying to make sure

[@tal4466]

Marco Sarmiento might be wrong...

[@shivshukla8013]

How about a problem asking distance/displacement?

[@CrazyShooter199]

"This is the purple area! :D That's not purple o.o" lol

[@blablasijus]

Train constantly accelerates from 40km/h to 80km/h. How do i find at which speed train was going at half the total distance traveled? Sry for bad english, i hope you guys understood my quoestion :S

[@skarpengland]

+Kūgis Mūgis um, i just started physics, but isnt that too little information? dont you need the time travelled as well?

[@skarpengland]

+Kūgis Mūgis i tried to solve it, did the train go at 60km/pr hour after half the total distance?

[@KingCitaldo125]

+Kūgis Mūgis first convert km/h to m/s use d=rt to find time. that should be your starting point.

[@megadeth1231]

because it wasn't constant 13m/s, it was from 5 to 13 thus making the distance less than 13*4

[@SuperLePATRON]

Black board is a bit hard on the eyes... Is there any possible way you can be using the white board? Please... Also the lesson are outstanding, really appreciated!

[@VSPG_SIVANI]

Many think black is a bit comparatively easy on eyes.

[@SuperLePATRON]

I must have sensitive eyes i guess.

[@iMusikkForeva]

+serge kas I actually love the black board...the white is too bright for me.

[@SuperLePATRON]

+iMusikkForeva Seems every like the black board... My eyes became colour sensitive after Lasik surgery a couple of years ago.

[@iMusikkForeva]

Wow, if you don't mind me asking....do you have any complications? I wear pretty thick glasses (-5.00 for each eye), and was considering lasik surgery next year as I'm going to turn 18. Is it going well for you?

[@ashraelll]

I don't get that end part about adding up the formulas and the average stuff

[@GfunkERA3131]

are you and patrick jmt homies? i sure hope so you guys are both awesome

[@stevec__]

I like this Khan guy

[@6thHorseMan]

Patrick JMT is top notch for math.

[@williamhusemoen-zhang5014]

I love you

[@FersotJ]

That formula (near the end) is just the formula for the area of a trapezoid. Why don't you know this Sal?

[@pairot01]

if everything was the same color then it could get messed up, he uses the same color for the same variable in the formulas, so helping you to keep track. if it was all one color it would just be like a blackboard and some people would find it boring as it resembles school, and also a lot of colors makes it eye catching and therefor making people want to see it when they see the thumbnails, it's helpful and also it's good marketing

[@fluffsnake]

What if the acceleration changes over time? Is there a video explaining how to calculate the average velocity then?

[@zlidyh5]

Look up riemann sums, you can take the integral of an equation to calculate area under a curve.

[@AhmedAshraf-gp8rs]

Thanks a lot, I have a question? How do we measure the displacement in 36 meters whereas displacement between VF and VI= 8 meter and slope= 8 meters because the acceleration moved 2 meters in 4 seconds so 2*4=8? So the slope = total displacement = displacement between VF and VI. How do we get The total displacement= 36 meters? I hope to understand.

[@ainjeffery]

As Sal wrote the equation at the end that: Change inT*1/2 vf+vi. And you can view that 1/2 vf+vi as average velocity which is also as "(vf+vfi)/2" so Sal actually took the average velocity from the whole graph which is 13+5=18/2=9 and the multiplied it by change in time 9*4=36 This all is just the common sense. You just take the average velocity of the "whole graph" and multiply it by the time which results in S=Change in time*Change in velocity. I hope it helped

[@朱彦旻]

why this is distance but not displacement?It actually has a direction.Anyone can answer my question,i will be very thankful.

[@MrDemi-wn8zw]

logic first !!

[@SIMRANKAUR-eg7nc]

Check these concepts guys. Such concepts r needed in exams like JEE NEET. Amazing. search shwetanki Singh

[@ernesthemingway4299]

is there a formula for this?

[@user-sp9nt7ys1q]

i couldnt understand anything im rly stbd

[@ciao_abhi]

its not V X T... this formula does work cuz it is for a constant velocity and NO acceleration... it becomes obsolete when you have acceleration... thus just know the formula khan showed u

[@Tplus10]

who dislikes these videos?????

[@firestormjupiter]

@TPlus Gaming hardly anyone

[@MagnusTheUltramarine]

Can someone help me with this..? When he factorised: Tx(Vi + 1/2Vf - 1/2Vi) Why did he keep the 1/2 of Vi? shouldnt it cancel with the other Vi. Suposse that Vi=2, then 2x2/2 is 2, Not 1/2x2... I dont really get that part

[@jannatulnaima4186]

Why S=vt and S= Ut+1/2 at2 dont get same distance when acceleration 9.8

[@starinsky2873]

I am gonna use arithmetic series to solve final velocity to let people know I am future scientist 😂😂😂

[@nikebballlove]

SOO CONFUSING!

[@khajarayees3498]

Please can any one tell me when velocity is constant average velocity and instantaneous velocity do they differ or same please help me

[@nolanbeck6913]

They are the same

[@amukhb8608]

You didnt even explain the slop in that graph and how to do it.

[@midnightsilverpuppy]

Wow

[@temamahmed6789]

wait a minute how did u add it u suppose to minus b/c when we criss cross the answer will be like 4*2 which is equal to 8 then Vf-5 *1 =Vf - 5 then 8=Vf - 5 shift 5 then it's like 8-5=Vf which is 3. btw so confusing

[@tal4466]

Temam Ahmed You don't subtract. Only subtract vf-vi for acceleration to find change in velocity.

[@kevinbs05]

Thank you, I've been wanting to integrate the entire time, just to skip everything.

[@MrShinobiguy]

ahhh so confusing with the meters per second per seconds and the accelration, slope, all its just a big mess

[@dragooner4]

i dont understand why you just dont integrate from 0 to 4 2x+5dt =(. The triangles and shape stuff is too complicated!!!!!

[@weirdotabo]

I don't mean to be judgemental or anything but just being completely honest, your I's look like J's. just an fyi. sorry for wasting your time... btw, this really helped me and I thank you for that. Common Core is crap let me tell ya. Ugh. #Khansaveslives

[@SonikPanther]

bruh its a bad j then cause its backwards

[@alandsoran5772]

I think u did something wrong because after starting to accelerate you actually travelled less distance in 4s then you did when the velocity was a constant 5m/s

[@alandsoran5772]

ow yeah thanks for replying forgot to delete this comment ;/ i watched the video again and understood what he was saying.

[@karimkarim8393]

Dont delete the comment, it will help others understand if they have the same issue.

[@gaudenciohernandez8916]

Mr. khan I admire you greatly, but I cannot agree with the result in this presentation. How can there be displacement of 20 meters at time ZERO. By definition at time zero everything starts

[@adamfernandez5435]

I was thinking the same thing. The initial is 5m/s why is he going below that. The answer should be 16m correct?

[@CB-rl6om]

Yes there was a mistake

[@FersotJ]

@Shadowriku40 OK. But at least acknowledge it next time Sal?

[@gaudenciohernandez8916]

SORRY, On second thought I SEE you are correct, my mistake of perception.

[@Devilonyx]

Well...its good but the thumbnails are damn scary!!

[@CringeCronge]

I'm color deficient! don't use purple and blue! :( haha

[@mansoorkhan8296]

Its blurrr

[@philoconnor7138]

Please stop with the colours. How about using only 1 different colour for something really important. Too many colours don't help at all cos everything starts looking like a christmas tree.