2-dimensional momentum problem (part 2) | Physics

2-dimensional momentum problem (part 2) | Physics | Khan Academy

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16 жыл бұрын

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We finish the 2-dimensional momentum problem. Created by Sal Khan.
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Пікірлер: 61

@Marcs099 6 жыл бұрын

I was wondering why it was at 240p and not a cool 720p (at least) then I realized it when he pulled up google's homepage..

@jamilamohammadi3247 3 жыл бұрын

I never knew YT had 10 min limit!

@hahs4 12 жыл бұрын

no one of the best thing about Sal's vids is that they are short this is much better

@TinyTurtie 14 жыл бұрын

thank you, finally an explanation of how this stuff works... magical...

@TheBinbalaboom 12 жыл бұрын

You literally saved my physics grade..... Seriously, God sent you to me from me breaking down and give up, take sleeping pills and just sleep. THANK YOU!!

@louza8 14 жыл бұрын

NLLA07, shorter vids are more easily digested and navigable. this method is far superior for learning sections of phys at a time, imo.

@GeorgeandDavis 14 жыл бұрын

You're vids are excellent!!! cheers :D

@saramgeorge 10 жыл бұрын

I used TOA trig rule instead of SOA to find the angle. My answer was 38.2º, so it was 0.5º different than Khan's answer. Is it wrong?

@Reydriel 9 жыл бұрын

Not really, it's just that his answer got affected by the rounding of the hypotenus length when he calculated it. Yours is probably more accurate :)

@mayko2468 6 жыл бұрын

SaraMGeorge I found the same thing, I guess it's only bcuz of using more or less precise numbers

@Cretan1000 12 жыл бұрын

Could 3d momentum equations also be solved like this, i.e. using the same principals but 3d trig equations at the end and finding the before and after momentum in the x,y, and z axis?

@SupremeCoalition 13 жыл бұрын

thank you mister!

@thevastuniverse246 4 жыл бұрын

Hello, U could have actually found the angle at the end of the video in a simple way, U can take the arctan of 2/2.54 Which simplifies to about 38.216 but u got about 38.7

@ernsaglam Жыл бұрын

they didn't have that technology 14yrs ago :)

@purplepick1 14 жыл бұрын

yea i love these vids

@pokemonfanrock1 11 жыл бұрын

1:27 ´´A´s momentum in the B direction`` best phrase ever

@fishomelette4871 9 жыл бұрын

Sorry, I'm really new to this so correct me if I'm wrong but if B (5kg) is travelling at 3.2m/s meaning its momentum is 16kg m/s and A (10kg) is travelling at 2m/s meaning its momentum is 20kg m/s wouldn't the total momentum not equal to 30kg m/s anymore? Or do you not add the two momentum together anymore since they are not moving in the same direction?

@MYHANDISADOLPHINLOL 8 жыл бұрын

+Fish Omelette The momentum vector is angled, so you can't really add them.

@jennyuzzy 15 жыл бұрын

lol...i kno, would hv gone thru sin-1 but your gr8. thnk you. really made a huge diff

@megaelliott 15 жыл бұрын

On the windows calculator, if you click view, then scientific you can actually get the inverse functions. Type in a number, click the inv button and then click sin.

@alanamolana9767 6 жыл бұрын

can you plz make a vedio on newton rings

@NinjaPicnicers 5 жыл бұрын

Holla if your out here in 2019

@jamilamohammadi3247 3 жыл бұрын

Hey! I'm writing from 2021

@lawlers3 11 жыл бұрын

No, only if the problem specifically states that the objects final angles create a complementary angle

@borisyadershik 13 жыл бұрын

super

@CaffeCraft 11 жыл бұрын

ues, it is possible, but it would require some quite complex matrixes or systems resolutions. doable, though, since the same laws of physics apply, only the mathematics that would get more complex

@ferociablejbear 15 жыл бұрын

yeah

@woodenjaw 15 жыл бұрын

Since the ball is going down and right, should Ball B direction be 321.3? (38.7-360)

@isam1335 14 жыл бұрын

@xofemaleraiderxo isnt that supposed to be -38.2 degrees?

@chendwachintu4429 9 жыл бұрын

you mean we draw the second vector starting from the head of the first, and they must be perpendicular to each other?

@LOLWAAHH 10 жыл бұрын

Why is the V(x) of ball b 2.54? I got 1.6, and then with the V(y), I found the resultant velocity as 2.54 m/s....

@Dundertaker 14 жыл бұрын

@NLLA07 This video is 2 years ago, so possibly it was different back then.

@doctormurray91 14 жыл бұрын

Same thing

@jean-nx5di 4 жыл бұрын

you can use kinetic energy to find the speed as well

@shagyy7449 4 жыл бұрын

he would find a speed, but he need velocity, he needs also direction of it. He cant do that with energy. But usually problems like this contain both energy and momentum

@FRUITT1018 11 жыл бұрын

4:13 - 7:34 is just simple trig and geometry in a physics based problem, lol. so basically, the physics part of these kind of problems is knowing the formula for momentum (P=m*v) and just setting it up (Px initial = Pax + Pbx and then Py initial = Pay + Pby) and the rest is trig and/or geometry love these videos, very helpful for my AP physics class in high school!

@SwellBread 12 жыл бұрын

I thought that B and A must create a right angle, post collision...

@NLLA07 14 жыл бұрын

There is technically not a really 10min limit people from Stanford University posted a 2hr lecture vid

@Mpb324utube 9 жыл бұрын

I agree with Omelette, P must be conserved. Since Pa(final) is given as 10*2=20, initial P=10*3=30, and to cancel out the vertical P of A & B after impact we got 2 m/s in the down direction (giving a Pb=5*2=10), then there is no Vbx since 20+10=30.

@alphalock1 9 жыл бұрын

I also agree with what both of you mean but there IS a Vbx and a Vby, I hope I can explain it and that it makes sense: for us to maintain Pa=30 throughout the whole equation we have to divide it into the 2 "paths". One is already given: P of a after hiting B is 10kg*2m/s=20. For us to maintain 30, Pb must be 10 right? 20+10=30 check. Mb*Vb=10 ---> 5kg*2m/s=10 Our Vbx+Vby velocity is 2m/s, which we have to brake down into the x and y components. Sinus of 30° is 0.5, which tells us the correlation between Y and X. If 20 is our whole Pa, then Pax has to be 2 times the value of Pay. So Pay is 6.67 instead of 10. If you calculate Vby with that number and then use sinus to calculate the last leg of the triangle you got: Vb=2m/s, being Vby=1.334 and Vbx=1.490 Now everything fits. The angle of B is roughly 42° . correct me if I'm wrong though.

@etruiste1738 9 жыл бұрын

Erik Fasterling Your saying what he did was wrong?

@isam1335 14 жыл бұрын

@xofemaleraiderxo counterclockwise..

@sarasrandomz 10 жыл бұрын

Could you PLEASE start writing 0.625 instead of .625?!!! I think you can all tell why I'm asking this... Thanks.

@OranJJeTofu 3 жыл бұрын

Why is it 2 m/s and not -2 m/s?

@MrRkesh 6 жыл бұрын

yu should turn up the speed

@Xclann 13 жыл бұрын

@NLLA07 They are youtube partners...

@isam1335 14 жыл бұрын

@xofemaleraiderxo sorry i mean clockwise

@12manganime 12 жыл бұрын

ur not the only one who thinks tht right now... :P

@fannthom 15 жыл бұрын

Sal. To be more accurate you shouldnt round off to 3.2. Leave it as 3.23, and you will get 38.2 deg

@LOLWAAHH 10 жыл бұрын

oops never mind, just a calculation error

@pball4lyfe72 12 жыл бұрын

idk which video is next ?!? :/

@imwithdumbhead 13 жыл бұрын

good explanation but dirty work.

@luyla1 12 жыл бұрын

SO U KNOW THIS ALL AND BECOME A TEACHER :(

@pwopwner 12 жыл бұрын

Mr.Khan, would there be a way that the youtube community could protest to get you a premium account? I am pretty sure that youtube has the power to upgrade you to putting hour long videos?