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

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

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13 жыл бұрын

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Calculating average velocity when acceleration is constant. Created by Sal Khan.
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Пікірлер: 141

@thedogdogification 3 жыл бұрын

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.

@paulschlacter2182 10 жыл бұрын

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 2 жыл бұрын

don't you think he is one too

@megashani91 11 жыл бұрын

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

@elviszhang2853 7 жыл бұрын

Khan is my savior

@baphnie 7 жыл бұрын

My secular thoughts exactly!

@seandimmock5813 5 жыл бұрын

Hail khan

@comrat9805 5 жыл бұрын

truth

@taylorg1113 4 жыл бұрын

Jesus*

@babatunde3775 3 жыл бұрын

@@taylorg1113 not everyone is christian fam

@jobairahmad742 8 жыл бұрын

you are blessings of today students

@mubarkas8876 11 жыл бұрын

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

@ItHappens117 13 жыл бұрын

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

@scottnorman1940 4 жыл бұрын

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.

@davisjohn1517 8 жыл бұрын

Thanks Sal! Great video, I learned a lot!

@monkezballs 7 жыл бұрын

This made it so clear. I'm truly grateful for this video series

@IBeExtraCool 11 жыл бұрын

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.

@ambers123100 11 жыл бұрын

Mr.khan, you are is man of awesomeness

@averygee794 7 жыл бұрын

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

@rizokhon5677 10 ай бұрын

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

@bestbrothersra6205 Жыл бұрын

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

@stevestadler4634 6 жыл бұрын

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

@Hino_55 4 жыл бұрын

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!!!

@iMusikkForeva 8 жыл бұрын

he's so amazing!!

@thomasgaertig9453 5 жыл бұрын

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

@maaaaddieee 11 жыл бұрын

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!

@pokeanalysis4917 8 жыл бұрын

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

@sushicartman01 12 жыл бұрын

Thanks man, you're sooooo helpful!!

@JohnDoe-ze8pf 11 жыл бұрын

I know right?! This guy is amazing.

@thinginground5179 2 жыл бұрын

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!

@bernardlz 6 жыл бұрын

Crystal Clear!

@sandeepsinghnegi2012 4 жыл бұрын

That's awesome explanation...ever

@davidbondy2250 5 жыл бұрын

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 4 жыл бұрын

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

@skeir4317 10 ай бұрын

This is amazing

@philliptubego3946 3 жыл бұрын

Topics are good

@DK-nz6bp 4 жыл бұрын

Thnx... Khan academy.....

@AlphaTesting 6 жыл бұрын

Beautiful.

@MRFARMS2 11 жыл бұрын

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

@Michael-cc4qf 6 жыл бұрын

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.

@nuzhatmirza9467 3 жыл бұрын

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

@gad416502 3 жыл бұрын

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

@guanatail 13 жыл бұрын

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

@CrazyShooter199 12 жыл бұрын

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.

@rrezonbeqiri5059 4 жыл бұрын

How can i solve for time with this formula

@dageron97 10 жыл бұрын

Shut Up and take my Physics Teacher!

@blueunicorngreencupcake6477 7 жыл бұрын

You should be our physics professor😂

@magicman198765432 11 жыл бұрын

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

@samus1225 11 жыл бұрын

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

@fleshcookie 12 жыл бұрын

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

@shivshukla8013 7 жыл бұрын

How about a problem asking distance/displacement?

@SomeRandomFellow 8 жыл бұрын

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 7 жыл бұрын

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

@shakinjunt 11 жыл бұрын

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

@jcen123 10 жыл бұрын

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

@uunz4435 9 жыл бұрын

What do you mean? African or European swallow?

@nuzhatmirza9467 3 жыл бұрын

I hope that is what you want

@Songohanssj2100 11 жыл бұрын

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

@AchiragChiragg 11 жыл бұрын

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 6 жыл бұрын

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?

@ciao_abhi 11 жыл бұрын

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..

@CrazyShooter199 12 жыл бұрын

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

@hellojennification 11 жыл бұрын

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

@MrDemi-wn8zw 10 жыл бұрын

logic first !!

@1ntelligentDiscourse 11 жыл бұрын

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.

@raynedeerman 12 жыл бұрын

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

@lokmanhossainlokman6422 4 жыл бұрын

Is it distance or, displacement 12:12

@user-ms7ti9ur5b 4 жыл бұрын

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

@stevec__ 6 жыл бұрын

I like this Khan guy

@ashraelll 7 жыл бұрын

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

@booklibrary2884 6 жыл бұрын

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

@drevil37373 11 жыл бұрын

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 5 жыл бұрын

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

@midnightsilverpuppy 7 жыл бұрын

Wow

@williamhusemoen-zhang5014 3 жыл бұрын

I love you

@6thHorseMan 12 жыл бұрын

Patrick JMT is top notch for math.

@Peter_1986 11 жыл бұрын

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.

@GfunkERA3131 12 жыл бұрын

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

@Hermon17yr 13 жыл бұрын

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

@blablasijus 9 жыл бұрын

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 9 жыл бұрын

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

@skarpengland 9 жыл бұрын

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

@KingCitaldo125 9 жыл бұрын

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

@SIMRANKAUR-eg7nc 3 жыл бұрын

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

@ernesthemingway4299 9 жыл бұрын

is there a formula for this?

@jannatulnaima4186 Ай бұрын

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

@khajarayees3498 9 жыл бұрын

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

@nolanbeck6913 9 жыл бұрын

They are the same

@megadeth1231 11 жыл бұрын

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

@FersotJ 13 жыл бұрын

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

@fluffsnake 8 жыл бұрын

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

@zlidyh5 8 жыл бұрын

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

@AhmedAshraf-gp8rs 7 жыл бұрын

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 7 жыл бұрын

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

@SuperLePATRON 8 жыл бұрын

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 8 жыл бұрын

Many think black is a bit comparatively easy on eyes.

@SuperLePATRON 8 жыл бұрын

I must have sensitive eyes i guess.

@iMusikkForeva 8 жыл бұрын

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

@SuperLePATRON 8 жыл бұрын

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

@iMusikkForeva 8 жыл бұрын

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?

@amukhb8608 2 ай бұрын

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

@Tplusclips10 6 жыл бұрын

who dislikes these videos?????

@firestormjupiter 5 жыл бұрын

@TPlus Gaming hardly anyone

@pairot01 11 жыл бұрын

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

@kevinbs05 12 жыл бұрын

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

@CringeCronge 4 жыл бұрын

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

@nikebballlove 11 жыл бұрын

SOO CONFUSING!

@MrShinobiguy 12 жыл бұрын

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

@starinsky2873 5 жыл бұрын

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

@user-sp9nt7ys1q 2 жыл бұрын

i couldnt understand anything im rly stbd

@gaudenciohernandez8916 6 жыл бұрын

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

@Devilonyx 13 жыл бұрын

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

@Dark4Sant26 10 жыл бұрын

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 6 жыл бұрын

Marco Sarmiento might be wrong...

@songerated2831 3 жыл бұрын

why is it 1/2?

@nuzhatmirza9467 3 жыл бұрын

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 3 жыл бұрын

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

@thinginground5179 2 жыл бұрын

@@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.

@dragooner4 12 жыл бұрын

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

@mansoorkhan8296 5 жыл бұрын

Its blurrr

@ciao_abhi 11 жыл бұрын

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

@FersotJ 13 жыл бұрын

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

@temamahmed6789 6 жыл бұрын

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 6 жыл бұрын

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

@gaudenciohernandez8916 6 жыл бұрын

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 5 жыл бұрын

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 5 жыл бұрын

Yes there was a mistake

@leyawonder2306 5 жыл бұрын

@alandsoran5772 8 жыл бұрын

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 8 жыл бұрын

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

@karimkarim8393 7 жыл бұрын

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

@weirdotabo 6 жыл бұрын

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 6 жыл бұрын

bruh its a bad j then cause its backwards