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!!
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
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?
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.
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.
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!
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.
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?
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
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
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?
![Yeat & Quavo - 5BRAZY [Official Music Video]](http://i.ytimg.com/vi/4XxnTAwyxus/mqdefault.jpg)
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..
no one of the best thing about Sal's vids is that they are short
this is much better
I never knew YT had 10 min limit!
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!!
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?
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 :)
SaraMGeorge I found the same thing, I guess it's only bcuz of using more or less precise numbers
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
they didn't have that technology 14yrs ago :)
NLLA07, shorter vids are more easily digested and navigable. this method is far superior for learning sections of phys at a time, imo.
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?
+Fish Omelette The momentum vector is angled, so you can't really add them.
Could you PLEASE start writing 0.625 instead of .625?!!! I think you can all tell why I'm asking this... Thanks.
1:27 ´´A´s momentum in the B direction`` best phrase ever
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.
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.
Erik Fasterling Your saying what he did was wrong?
thank you, finally an explanation of how this stuff works... magical...
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!
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.
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?
You're vids are excellent!!! cheers :D
Holla if your out here in 2019
Hey! I'm writing from 2021
lol...i kno, would hv gone thru sin-1
but your gr8. thnk you. really made a huge diff
thank you mister!
No, only if the problem specifically states that the objects final angles create a complementary angle
can you plz make a vedio on newton rings
Since the ball is going down and right, should Ball B direction be 321.3? (38.7-360)
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
you mean we draw the second vector starting from the head of the first, and they must be perpendicular to each other?
you can use kinetic energy to find the speed as well
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
yea i love these vids
There is technically not a really 10min limit people from Stanford University posted a 2hr lecture vid
super
@xofemaleraiderxo isnt that supposed to be -38.2 degrees?
I thought that B and A must create a right angle, post collision...
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....
@NLLA07
This video is 2 years ago, so possibly it was different back then.
Why is it 2 m/s and not -2 m/s?
yeah
Sal. To be more accurate you shouldnt round off to 3.2. Leave it as 3.23, and you will get 38.2 deg
Same thing
@NLLA07
They are youtube partners...
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?
yu should turn up the speed
@xofemaleraiderxo counterclockwise..
ur not the only one who thinks tht right now... :P
@xofemaleraiderxo sorry i mean clockwise
oops never mind, just a calculation error
idk which video is next ?!? :/
good explanation but dirty work.
SO U KNOW THIS ALL AND BECOME A TEACHER :(
how can the angle be 38.7 degrees in a right triangle? doesnt a right triangle consist of angles that are 45 45 90 or 30 60 90?
Those are special right triangles. A "right triangle" is any triangle with a "right angle" or 90 degrees.
you could have 90, 89, and 1 as the three angles if you wanted
you could have 90, 89.9999999and 0.0000001 as the three angles if you wanted
i like to play with my xbox 360