You have two angles: A=40° and B=60°. You have three sides: a, b, and c=12kg=117.6798N. You actually have three angles: C=80°. a/Sin(A) = b/Sin(B) = c/Sin(C). 117.6798 / Sin(80) = a/Sin(60). a = Sin(40)*117.6798/Sin(80) = 76.81 a = 76.81N. b = 103.4859N. c = 117.6798N. sqrt(76.81^2+103.4859^2 - 2(76.81*103.4859)cos(80deg)) = 117.6798. If you have two sides and an angle opposite an unknown, law of cosines does it every time. If you have a side with its opposite angle and any other side or angle, law of sines gets you the entire triangle. Also his answer is incorrect.
@@johnmoser3594 In components Trigonometry applies or you can resolve using cosine law. Sin law can lead to the ambiguous case solution so the latter is not recommended.
Thank you so much. You have made this straight forward and to the point. Also, you're the first person whose video I've seen that does not use matrices to solve this. Thank you again.
MrPAINNY When you solve for B in the equation 1.97B=117.6N, you get B=117.6N/1.97, which then means that B=59.7 then since A=1.532*B, you plug in your B (this was 59.7) and you get A=1.532*59.7=91.5
Instructor helps one to see a steeper angle on one of the cables bearing the weight means this cable needs to be stronger strand wise since it will carry more of the twelve Kilograms. Hopefully this analysis is correct.
The force for vector C, in this example, will always be the weight of the object. Now remember that the NET FORCE on the object is zero. If it wasn't zero, then the object would be accelerating!
Thank you for viewing the video. At 4:45 I determine that A=1.532B, so after I figure out that B=59.7, I plug that in: A = 1.532 X 59.7 . That better equal 91.5 :) .
Review your trigonometry. Acos60 represents the x component of vector A (Ax). The vector flashes when I put the Acos60 up on the screen. Since the x component is adjacent to the angle, I use cos. Explicitly: cos60 = adjacent side/hypotenuse so cos60= Ax/A or solving for Ax: Acos60=Ax.
Thank you for viewing my video. At around 5:49 I show how I get B. I then plug that value into the equation for A (A=1.532B, in orange color) above to get A There is quite a bit of algebra in simplifying the B equation, so you may have to watch that part a couple times. Write it out yourself for maximum benefit.
What would you do if there was a third cable that was just going straight down to the load? I know the forces in the X direction wouldn't change, but I don't know how to balance out the forces in the Y directions
PhunScience Okay then lets say the load is N and its being held up by three cables. Cable 1 is in a straight line from the load to the horizontal. Cable 2 is 30degrees on the left from cable 1 and cable 3 is 30degrees on the right of cable 1. Showing the cables to be in symmetry with cable 1 being the axis of symmetry
our teacher linked us this video but i have no idea what it is that we're trying to find here... are we finding the tension in each string??? or is it something else?
PhunScience I get everything now! You explained everything clearly, no wonder my teacher linked us your video out of all the ones on youtube. Thank you so much for uploading this!!
The y component of vector B, Bsin40, lies along the positive y axis (see the green vector component) so it is positive. The x component of vector B, Bcos40, lies on the negative x axis, so it is negative. The y component though, is positive as described above.
Sure. At 5:30 I start solving for B. The equation is 1.532Bsin60 + Bsin40 = mg. I then factor out the B. You can see the result appear at 5:34: (Remember that 4x + 2x is the same as x(2+4) )? The equation as shown at 5:34 is then this: B(1.543sin60 + sin40) = mg. At this point you can calculate the terms in the parentheses and get 1.979 and and also mg= 12 x 9.8 . You now should have: B(1.979) = 117 . Divided both sides by 1.979 and you get 59.1 . Hope this helps.
Great job. However, it is much easier (and simpler) to solve these types of two-cable support system using simultaneous equations. We have two equations in two unknowns and using simultaneous equations, or matrices, we can solve this in a matter of 1 to 2 minutes.
Has anyone figured out how to solve these problems yet, or are we all still doing a half a page of vector decomposition into multiple right triangles? This guy is solving a system of simultaneous equations, which might be an even worse approach.
In this particular example, there are two unknowns so simultaneous equations have to be used. This example, I believe, is the most difficult problem a high school student (the intended audience) is likely to see.
sir is this right?? first i try to get the downward force or the (f=mg) the i divide it by two and distributed it to upward force A and B and uply the trigonometry .. my answer is A=91.5N but B=67.9N...
No that is not correct. You can't divide the weight (mg) by two and distribute to the two upward forces because the angles are not the same. Try following the steps I use in the video.
@@PhunScience I'm sorry sir but I gonna need more of your patient and time if it's OK with. How did you get this 9.8 m/s^2 hope you will give me more time to figured out my messy brain I'm sorry sir thanks
@@johnryanalegre2753 The 9.8 is a constant. If you drop an object on the Earth, it will accelerate at 9.8 m/s2. On the moon things will accelerate at 1.6 m/s2. The acceleration is due to the force of gravity. Weight, which is the force of gravity on an object, is defined as mass x g. You can easily 'Google' terms like 'g' and 'acceleration due to gravity' or "weight", to further your understanding.
oooh he replied... I did not expect that! But thanks for this video I was having trouble understanding this concept as I do online school and have been rushing through school as I am graduating a year early from HS. Thanks so much for this video though!
God bless you kind sir. If only my professor could explain as well as you.
savannahissavvy
do u know the moment & couple force of physics
my final exam is near,
but I don't understand how to solve this physics...
??
You have two angles: A=40° and B=60°. You have three sides: a, b, and c=12kg=117.6798N.
You actually have three angles: C=80°.
a/Sin(A) = b/Sin(B) = c/Sin(C).
117.6798 / Sin(80) = a/Sin(60). a = Sin(40)*117.6798/Sin(80) = 76.81
a = 76.81N. b = 103.4859N. c = 117.6798N.
sqrt(76.81^2+103.4859^2 - 2(76.81*103.4859)cos(80deg)) = 117.6798.
If you have two sides and an angle opposite an unknown, law of cosines does it every time. If you have a side with its opposite angle and any other side or angle, law of sines gets you the entire triangle.
Also his answer is incorrect.
John Moser
its already solved,,,,,
now, I have big problem
about gravity
@@johnmoser3594 In components Trigonometry applies or you can resolve using cosine law. Sin law can lead to the ambiguous case solution so the latter is not recommended.
You probably won't read this ever but seriously thank you. What took me hours to understand took minutes with you explaining it.
Thank you so much. You have made this straight forward and to the point. Also, you're the first person whose video I've seen that does not use matrices to solve this. Thank you again.
I wish my statics teacher could explain it this well, thank you very much
Thank you. This concept was very confusing to me until I watched your video. You did a terrific job of explaining it.
I struggled so much to understand this in class and when I found your video, it all made sense. Thanks for explaining so well and clearly!
this is the first physics video that made me understand physics way better . thank you very much for your work , god bless you
Absolute hero. You have made this so easy! Thanks.
+John Horrill Yeah, everything here is so organized it was all clear to me.
He is also my absolute hero.
Thanks for this video! I was able to get the concept of all static equilibrium problems based solely off your help! :)
Great video. Your videos are helping me maintain an A average in a class that I usually have great difficulty in. Keep em' coming!
Amazing tutorial, I would have never been able to understand Statics. Thank you!
You Are a professional professor
how did you get that 59.7N and 91.5N?
MrPAINNY When you solve for B in the equation 1.97B=117.6N, you get B=117.6N/1.97, which then means that B=59.7 then since A=1.532*B, you plug in your B (this was 59.7) and you get A=1.532*59.7=91.5
Thank you SO freakin much... the only video I have found that makes sense!!!!
Thanks for posting this video! It's helped me learn more about static equilibrium, because my textbook is overcomplicating things.
its 2020 and this is still helping thank you sir
This video saved by butt. You're an amazing person.
Megan Potato Is potato actually part of your name? Just curious...
Moreover Instructor definitely affords us his salvation. Thank you Sir
nice job mate i was struggling with these but finally i now know how to do it thanks:))
Thanks, this video helped out a lot. Explained really well.
The hero we need but not the one we deserve
Great explanation, thank you.
Thanks you save my butt to my periodic test yay
geeenius way of explaining!! thank you so much, finally able to solve it as well :)
Instructor helps one to see a steeper angle on one of the cables bearing the weight means this cable needs to be stronger strand wise since it will carry more of the twelve Kilograms. Hopefully this analysis is correct.
Hi was just wondering how you got the answer B=59.7? I am struggling to work the equation out and wondered if you could extend on this. Thanks
BEST teaching vid. life saver. thank youu
very good job.. wish i would've saw this before my last test!!
Not all heroes wear capes!! who else here has an exam tomorrow?
Does this mean that Even with or without the 3rd string. The force on C is the same?
The force for vector C, in this example, will always be the weight of the object. Now remember that the NET FORCE on the object is zero. If it wasn't zero, then the object would be accelerating!
Thank you very much, this helped me a lot!
Thank you for viewing the video. At 4:45 I determine that A=1.532B, so after I figure out that B=59.7, I plug that in: A = 1.532 X 59.7 . That better equal 91.5 :) .
PhunScience so after getting
B(1.532sin60+sin40) = (12kg)(9.8m/s/s)
=
1.97=117.6
To get B=
117.6divided by1.97 = 59.7?
THANK U SO MUCH SIR I SWEAR IM IN EIGHTH GRADE AND IVE NEVER BEEN HAPPIER THAN TO UNDERSTAND EQUILIBRIUM! GOD BLESS YOUR GOOD SOUL!
The sum of the two tensions don't equal the net force of the weight. Are they supposed to?
No they should not. If you look at their y-component vectors you'll see that THEY equal the weight.
Oh okay. Thank you!
Thank you v much
It was way clear and easy to understand
how did you get 91.5 N in Tension A?
I took the value for B and plugged it into the equation above A=1.532B , shown at 4:53 of the video.
+PhunScience just like you did in Fsub Y
+Joseph Escorel not sure what you are asking, but I found B=59.7... then A=1.532 x 59.7...
how do you know when to use sine or cosine? and when you did Acos60 what does that represent or solve? sorry if my question doesnt make sense
Review your trigonometry. Acos60 represents the x component of vector A (Ax). The vector flashes when I put the Acos60 up on the screen. Since the x component is adjacent to the angle, I use cos. Explicitly: cos60 = adjacent side/hypotenuse so cos60= Ax/A or solving for Ax: Acos60=Ax.
PhunScience i understand it now, i didn't realize the part about solving for ax! thank you sir
"Y sin when you can have Cos x?" is a fun phrase to remeber it.
Read it as "Why sin when you can have (co)sex?"
Sin goes with y, Cos goes with x
***** Lol. Cool phrase. I'll probably use that if I ever forget.
How did you get b and a at the very end?
Thank you for viewing my video. At around 5:49 I show how I get B. I then plug that value into the equation for A (A=1.532B, in orange color) above to get A There is quite a bit of algebra in simplifying the B equation, so you may have to watch that part a couple times. Write it out yourself for maximum benefit.
What would you do if there was a third cable that was just going straight down to the load? I know the forces in the X direction wouldn't change, but I don't know how to balance out the forces in the Y directions
Any forces going straight down would be subtracted from the forces going up, just like the weight is subtracted.
I understand, I guess my real question is what would you do when you now have 3 unknowns and only 2 equations.
In that case, I don't think you could solve it. Then again, I'd have to see the particular problem to determine if you are overlooking something.
PhunScience Okay then lets say the load is N and its being held up by three cables. Cable 1 is in a straight line from the load to the horizontal. Cable 2 is 30degrees on the left from cable 1 and cable 3 is 30degrees on the right of cable 1. Showing the cables to be in symmetry with cable 1 being the axis of symmetry
rafedanny Also both cable 2 and 3 are the same length.
2:20 Sometimes they give the weight in lbs because the US is a country that refuses to accept that metric system is the best.
Thank you very much! It really helps me a lot!! Please then post the trigonometric equation of this thank you!
our teacher linked us this video but i have no idea what it is that we're trying to find here... are we finding the tension in each string??? or is it something else?
Hi. You are correct. Find the tension in each string.
PhunScience I get everything now! You explained everything clearly, no wonder my teacher linked us your video out of all the ones on youtube. Thank you so much for uploading this!!
Excellent. Thank you.
I used lami's theorem to solve this and got T.a=58N and T.b=90N. (Calculated roughly ,decimal omitted).
In the vertical sum of force formula why is it +Bsin 40; isn't the force in the negative side?
The y component of vector B, Bsin40, lies along the positive y axis (see the green vector component) so it is positive. The x component of vector B, Bcos40, lies on the negative x axis, so it is negative. The y component though, is positive as described above.
Sure. At 5:30 I start solving for B. The equation is 1.532Bsin60 + Bsin40 = mg. I then factor out the B. You can see the result appear at 5:34: (Remember that 4x + 2x is the same as x(2+4) )? The equation as shown at 5:34 is then this: B(1.543sin60 + sin40) = mg. At this point you can calculate the terms in the parentheses and get 1.979 and and also mg= 12 x 9.8 . You now should have: B(1.979) = 117 . Divided both sides by 1.979 and you get 59.1 . Hope this helps.
And how do you figure out B=59.7?
Great job. However, it is much easier (and simpler) to solve these types of two-cable support system using simultaneous equations. We have two equations in two unknowns and using simultaneous equations, or matrices, we can solve this in a matter of 1 to 2 minutes.
shouldn't 40° be written as 180-40 as it is in different quardant
how did you get the (A=91.5)?
Would it not be simpler to just make the y axis equal to mg then do Acos30=mg and Bcos50=mg?
Oh its the same answer nevermind
Why do you subtract the x component of A from the x component of B?
It is subtracted because it lies on the negative X axis.
Has anyone figured out how to solve these problems yet, or are we all still doing a half a page of vector decomposition into multiple right triangles? This guy is solving a system of simultaneous equations, which might be an even worse approach.
In this particular example, there are two unknowns so simultaneous equations have to be used. This example, I believe, is the most difficult problem a high school student (the intended audience) is likely to see.
Is there a reason why we use x instead of y in forces
I would like to help, but I don't understand exactly what your question is.
Excellent Sir . Regards
At about 5:30 there is an equation that contains B . You'll have to work on your algebra and when you solve for B you get 59.7.
sir is this right?? first i try to get the downward force or the (f=mg)
the i divide it by two and distributed it to upward force A and B and uply the trigonometry .. my answer is A=91.5N but B=67.9N...
No that is not correct. You can't divide the weight (mg) by two and distribute to the two upward forces because the angles are not the same. Try following the steps I use in the video.
thank you sir. it helped a lot!
Are you from New York?
joseph diaz No. Massachusetts...although currently in NC
How did u get A if u didn't find B.
5.43
Green Roberts I solve for B between 5:30 and 6:00.
@@PhunScience oh i see u common factor the b
thank you so much Sir!
my God bless you
To get B at the end; 117.6dividedby1.97= 59.7
And to get A; 1.532x59.7= 91.5
you are the best!!!
you are god sent, this video really helped me, consider me as a new subscriber. i will share this video
Goodmorning sir were did you get the (12kg)(9.8 m/s^2
It is the force of gravity (weight) due to the block. Weight= mass x g
@@PhunScience thanks sir. But how about 9.8m/s^2 sir?? Where di you get that one?
@@johnryanalegre2753 That is the value for 'g', the acceleration due to gravity on Earth.
@@PhunScience I'm sorry sir but I gonna need more of your patient and time if it's OK with. How did you get this 9.8 m/s^2 hope you will give me more time to figured out my messy brain I'm sorry sir thanks
@@johnryanalegre2753 The 9.8 is a constant. If you drop an object on the Earth, it will accelerate at 9.8 m/s2. On the moon things will accelerate at 1.6 m/s2. The acceleration is due to the force of gravity. Weight, which is the force of gravity on an object, is defined as mass x g. You can easily 'Google' terms like 'g' and 'acceleration due to gravity' or "weight", to further your understanding.
Hope you're my teacher in Physics😭 Our professor just keep things more complicated pfft
should you calculate in radians
Degrees
So helpful thank u sir !!
damn this is easy nice and simple bro
Thanks a lot!
You’re a goddamn lifesaver
Thank you! Why can't all these TH-cam teachers be my school teachers?
Thank you!
I appreciate the video!
1.532 x 59.7 = 91.4604
A = 91.5N
1.97B = 117.6N
117.6N/1.97B = 59.69543147
B = 59.7N
god bless you
you are amazing
This video rocks!
Thank you sir very nice..
Excellent !! I could did it by myself :D...
Excellent
thank you kind, kind sir
thankyou so much!!!!
Thankyu so much
I like how people are posting comments when this came out 6 years ago....
Ah, but I still read them and answer their questions should they have one. :)
oooh he replied... I did not expect that! But thanks for this video I was having trouble understanding this concept as I do online school and have been rushing through school as I am graduating a year early from HS. Thanks so much for this video though!
You're welcome!
Great !
Love it!
Thank you sir.
Thanks.
Thanks
thankz...
please uploade more videos
thanks PhunScience
"Stop moving"
Hi was just wondering how you got the answer B=59.7? I am struggling to work the equation out and wondered if you could extend on this. Thanks
Thanks a lot!