Trusses Method of Sections | Mechanics Statics | (Solved examples)
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- Опубликовано: 7 авг 2024
- Learn to solve for unknown forces in trusses using the method of sections. We go through multiple examples, step by step, using equations of equilibrium and moment equations.
🔹 Solve trusses using method of joints: • Trusses Method of Join...
🔹 Break forces into components: • Vector Addition of Cop...
🔹 Finding moments: • Moment of a Force | Me...
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Intro (00:00)
The Howe truss is subjected to the loading shown. (01:46)
Determine the force in members BE, EF, and CB (05:25)
Determine the force in members DC, HC, and HI of the truss (07:55)
Determine the force in members JI and DE of the K truss. (09:40)
Find more at www.questionsolutions.com
Book used: R. C. Hibbeler and K. B. Yap, Engineering Mechanics Statics.
Hoboken: Pearson, 2017.
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At 9:08, there is a typo. F_HI = 42.5 NOT 45.2.
I thought I was losing my mind when I solved it myself and watched it back, thanks for clarifying, and thanks for the great video.
@@remyfru You're very welcome :)
My professor's lecture video was 45 minutes long, but this 11-minute video was elaborated well. Thank you.
You're very welcome! I try to make them as concise as possible.
Wish my $2500 a semester could go to this guy instead of the professor that blabbers about how easy it was for them when they took the class 30 years ago. This guy is goated fr fr :0
@@zacharyfrederick5494Mine is $3000 a semester and our professor just blabbers useless stuffs 🥲
Thank you so much. You don't know how much you've helped me tonight ♥️
You're very welcome! I am really glad to hear this helped :) ♥️
Thats what she said💀
Oh My God . This Lockdown means free time and your channel means free great quality explanation . Thank u so much 🌹. Enjoying Mechanics . ❤️🥰
Glad to hear you enjoy mechanics. ❤️ You're very welcome and I hope you learn lots!
Great video, clear explanation of how and why to use this method. Basically a time-saver for convenience sake is what I get from it. Understanding this method also boosts your insights and understanding of statics
Glad it was helpful! Keep up the great work and best wishes with your studies.
This was so helpful! Thank you for your easy explanations
You're very welcome. Glad to hear it was helpful
انا عربي اشكرك على جهودك هذه ولك التوفيق ان شاء الله في الدنيا والأخرة
I am an Arab. I thank you for your efforts. May God grant you success in this world and the hereafter
You're very welcome! keep up the awesome work with your studies.
Such a good video. You just earned a subscription. Keep them coming!
Thanks for the sub!
thank you so much for this, just the right time i found your channel before our quiz tomorrow!
Glad I could help! I wish you the best on your quiz tomorrow :)
Another amazing video, thanks for the extra help with studying this stuff! 🙌
My pleasure! Keep up the good work with your studies.
God bless you! your videos are extremely helpful! Thank you so much!
You're very welcome! :)
thank you for this, the best explanation so far.
You're very welcome! Best wishes with your studies :)
Thank 👍you for your excellent presentation
You're very welcome!
Amazing Video, All doubts cleared
Glad to hear that :)
Thanks man, you're the best
You're very welcome!
You are the best! Thank you so much brother
Happy to help and best wishes with your studies!
Thank you soo much this video really helped me !!!
Really glad to hear that! Keep up the great work :)
thank you so much for existing. I promise you one day when I become a successful civil engineer I will contact you surely and thank you for every help u did throughout my engineering program. Just remember me. I am taking a screenshot of this comment.
You’re very welcome. I’m glad to hear that you’re pursuing your dream of becoming a civil engineer. I’m sure you’ll do great things in the future. I appreciate your kind words it means a lot to me. Best wishes :)
Super Helpful
Glad to hear :)
You are the best!!!
Many thanks :)
The example my professor gave only had 1 external force, so i didn't know that I had to calculate the moments of the other downward forces
Thank you
You're very welcome. I try to pick at least 3 examples to remove any confusions in students. :)
Absolutly the best truss video woooooow great
Thank you, I hope it was helpful to you. Best wishes with your studies!
Thank you i understod verey well
Glad to hear!
thank you needed this
You're very welcome! :)
Thank you for ur help 🤗👏
You're very welcome!
Thank you so much, while cutting section, can I make a slanted (diagonal) cut to avoid solving for member that I really don't need for problem?
Yes, you can cut vertically, horizontally, diagonally, etc. 👍
@@QuestionSolutions Thank you
Thanks very much,qm from Ethiopian 🇪🇹
Keep it up
You're very welcome!
I should be paying you my college tuition
How am I paying some boring dude to tell me about physics in the most unstructured way at 8am for $1800 when you just make it so simple and quick.
Hats off
Thank you very much. I hope you do amazingly on your courses and I wish you the best! Keep up the great work :)
This man is a legend
Thank you very much!
It is the best channel I have seen. Greetings from Iraq 🥀♥️🎉
Thank you very much! :)
Really really great content..... I also want to learn such kind of animation ....can you please tell me how you do it? It would be great help to me....love from India.
I use after effects for animations. There are tons of really good tutorials on youtube, so please take a look :)
@@QuestionSolutions thanks a lot... The very first channel which I shared on my social networks.... Keep doing...... You will certainly hit the market.. 😀
@@mohammadashu8984 You're very welcome. Sometimes, Udemy has free courses on after effects as well, so keep an eye out. Thank you so much for the share, I appreciate it. 😁
it was helpfull thanks
You're welcome!
Top much explanation sir❤
Thank you very much! ❤
Thank you so much. I have a question regards problem 2. To find Force AB can we use the moment around F? and why did you use the sum of Fy not continue using the moment to figure out the other sections. I used moment around F to find AB but ending up with different answer. Thank you
Can you please give me a timestamp so I can look at the spot you're referring to? Many thanks!
Great video, thanks! Just a quick question, I tried solving the 4th problem but using the other side of the cut and the answer is different. Is my answer wrong or is it possible to have different answers when using different equations?
Regardless of the cut you use, or which side you use, you should end up with the same answers. This can be verified by solving the whole truss. There is probably some numerical error. :)
you ae the best problem solver 10Q
You're welcome.
I'm glad I'm watching this video, I'm having my mechanics exam next week. But I feel you're a lil bit fast in explaining, seems quite difficult to catch up mentally. Like, before I process a part, you'd have gone 3 parts. Also, can you help write the equation one by one. You have real good content, but just to avoid confusion.
I try to keep these videos concise, so it doesn't take up too much time. It can be difficult, especially when being introduced to the subject for the first time. So I will keep what you said in mind, but try to watch the video a few times, or try to solve these questions by yourself first, and if you get stuck, then try to see what I did to get to the next part. These videos are meant as a supplemental tool, and not a substitution for a textbook/professor. Thank you for the feedback!
My approach to his every vid is to try to deeply understand the underlying concept and pause right at the very beginning of each example and try to think thoroughly on how to solve it myself. Give yourself some engagement on critical thinking rather than just "watching". Critical thinking will give you a solid comprehension of the topic that will stuck on your mind that would greatly help you on your exam and even after semester, you will still understand the topic. Works for me 100% I usually answer his examples on all statics vids 95% before he explains. Try it urself :)
Just wondering for moments how do you determine the direction for them?
Please kindly watch this video: ruclips.net/video/QNNnPZ68STI/видео.html
So initially, when writing a moment equation, I pick clockwise to be positive (this is an assumption). So you're looking to see, if we apply a force at a location, will that member turn clockwise about the point where we are calculating the moment at, or counter clockwise. If it's clockwise, its positive, if its counter clockwise, its negative (because it's opposite to our assumption).
The first 2 examples in the link I provided will help out a lot with directions.
Tried to find a video about moment equations like the one at 2:00, do you have any walkthrough videos on theese? :)
Please see: ruclips.net/video/QNNnPZ68STI/видео.html
I go through the basics of moments.
thank you sir....
You're very welcome!
For question one I know u take thr moment at Point B but if we took the moment at point H, we would have two unknowns, Fbc and Fbg horizontal component both causing a moment. How would u solve it then?
The whole point of taking a moment about a specific point is to eliminate as many unknowns as possible. If you have 2 unknowns after writing a moment equation, then you'd need another equation, probably for vertical forces or horizontal forces. Try to take moments about points that lead to direct answers.
thank you
You're welcome!
@9:12 Force in HI member would be 42.5 kN
Yup, there is a typo. Thank you for pointing it out.
Thanks for the video!
But I have a question for finding force BF in the second problem. If we would have isolated joint B, equilibrium along forces at x would be 10kN - 45Kcos(45) - F(bf) = 0. Hence i thought that force BF would not be zero. Im confused how this works ://
I encourage you to actually isolate for joint B and solve this problem. For your equation, you should have 4 forces. The 10kN, BG, BF, and BE for horizontal components (along x).
For the 3rd problem. The Force HI is 42.5.
Thank me later.
👍
yeah.. this should be pinned. It can also be obtained by applying summation of moment at A.
thanks i thought i got it wrong
can you help me with the second question.is Fbg not supposed to be cosine for the moment because the Fbg sine is going towards the pivot which will cancel.asking just to be sure
No, it's sine because that gives you the x-component. So you need to look at the sides from the angle. The opposite side to the angle gives you sine, which in this case, is the x-component of FBG. Cosine would give you the y-component, which wouldn't create a moment.
Hello, thanks a lot for this video. It was very helpful. I have a question: 5:35 can we cut the truss through BF, AG, AB? basically diagonally
You can pretty much cut it anyway you want (as long as you have enough info to solve it). The cut should be made to figure out the unknowns you want, so try to cut the ones you need to find. So yes, you can cut it diagonally 👍
@@QuestionSolutions ohh I see, thanks a lot and THANK YOU SO MUCH FOR THE INSTANT REPLY I admire your dedication💙💙💙
@@sapphireblue9209 You're very welcome. Best wishes with your studies!
@@QuestionSolutions thank you very much!
YOU ARE A FUCKING HERO DUDE!!!
Thank you very much!
Quick question: at 2:04, how do we immediately know that there won't be any reaction on the horizontal axis?
Like I can see that none of the applied forces have horizontal components, but couldn't AH (for example) cause a horizontal reaction from the support?
Thanks!
So when you're solving for the reactions at a support, we don't care about internal members. They don't make a difference since we think of the object as a whole. So all the purple forces are external forces, but we have no forces applied in the horizontal direction. Let's say we had a horizontal force applied at point F, in that case, we would have an AX reaction countering the force applied at F. It's the same if we had a simple beam resting on top of supports. We just solve based on external forces, what happens inside the beam doesn't matter.
Another way to think about it is to realize that while there is a force in member AH, that force goes from H to A and A to H, there by causing equilibrium. So to recap, when you are finding supports, internal forces do not matter, only external ones.
@@QuestionSolutions Wow, thanks for the detailed response! Makes a lot more sense now :)
@@benjaminyellin5095 Really glad to hear it makes more sense. Best wishes with your studies :)
For the question at 5:25, why does the force in member BA not equal the reaction force from point A?
I found a reaction force from joint A of 45kN when taking moments about point G, but the force in member BA is 50kN.
The cut was made above the reactions so they were not needed. No calculations were made to figure out the reactions at A, or G. Also, where did you get that BA is equal to 50kN? At 7:07, we find that BA = 45kN.
@@QuestionSolutions Thanks for your quick response!
I wanted to verify that the force in member AB equaled the vertical reaction force at A. I understand that it is not directly relevant to the section method.
I just checked my calculations for some of forces in the Y axis, and I totally forgot to include the 5kN on point E. Now I have the correct solution for AB.
Thanks again for the brilliant video!
@@milesbrack9188 Okay, glad to hear it was cleared up. Keep up the good work and best wishes with your studies :)
Watching this before exam is worth :)
Best wishes with your exam! :)
thank you
You're very welcome!
@10:37 shouldn't the answers be in kN not N as the original forces are in kN? Great videos and easy to understand and work through to show workings.
Yes, it's a typo. 👍
6:15 is it also possible to find the moment about point C since it also helps us get rid of F-BA?
Yes, you can write a moment about any point you want. The goal is to eliminate as many unknown forces as possible.
just to be sure is it not supposed to be cosine on the second question Fbg since the Fbg sine will cancel at the pivot D.asking just to be sure
You are calculating your components incorrectly. Cosine would give you the y-component, in other words, the vertical component of force FBG. Sine would give you the x-component, the horizontal component.
Has anyone ever told u ur a life saver?🥺🥺
I think I heard it about 3 times now, from very kind people like you leaving nice comments. Thank you, it made my day! Best wishes with your studies.
@@QuestionSolutions thank you!... and ur very welcome ❤️
@@OGTennyson ❤
@@QuestionSolutions I watched like 10 of ur videos already and it's so damn informative. U got a new subscriber my friend...keep up the good work on the videos bro ✅❤️...I rlly hope one day I'll make it as a civil engineer and be able to donate cash to ur channel because I feel ur teachings are highly underrated and I wouldn't want you to stop 😭. Keep the videos coming bro...imma be here 4 a while❤️
@@OGTennyson Thank you very much! Don't worry, you will make it as a civil engineer, you'll do great. Keep up the great work, do as many questions as you can, and use every resource out there to help you succeed. Especially those office hours from professors. 👍
at 8:49 , can we know wether we need to x eithr clockwise or anti clockwise because my answer 345 for fdc
It doesn't matter which way you assume it, if you get a negative answer, it'll be opposite to your assumption. So here, I picked it going towards the pin, but assume we did the opposite. Then the only thing that changes is that instead of -F_DCsin53, you would get +F_DCsin53. Which would yield a negative answer, and that means your assumption is incorrect. If you get 345, you made a numerical error, please double check your work.
You are my hero! Could you also make a playlist about Strength of Materials?
Yes, that is also on my list to do :)
@@QuestionSolutions pls do it soon. love your videos btw
@@ElCrankoPunko Unfortunately, Strength of Materials won't be done for some time. The next topic is thermodynamics. I think there are a lot of videos on RUclips about material science, I hope they can be helpful.
@@QuestionSolutions cool man. eagerly waiting for thermodynamics videos :)
@@ElCrankoPunko :)
9:28 wouldn"t that be that Fx= -Fhc - (-125)sin 53.13 = 100 (T)? Since the direction is in the opposite of the assumed direction and the Fdc is compression so its negative (-)?
If the force comes towards the pin, it's in compression, if the force leaves the pin, it's in tension. Please see: ruclips.net/video/_rK02neOF18/видео.html
At 2:00 why there's a two forces in joint A, there's already a 2kn downward load why we have to put Ay in solving moment
That's a support reaction. So it's a pin support there, and that means there is an Ay component along with an Ax component. However, the ax component do not create a moment about point E.
how do you assume the direction of forces, like how do you determine where will the arrow point at? btw great vids man very helpful
That's completely up to you. If you watch this video, I go over how that works: ruclips.net/video/_rK02neOF18/видео.html
Check me if I am wrong,you said if we chose the moment at 1 point then we can eliminate the action force acting on it,but I don understand in 2nd example at 6.30 ,which moment at point D ,the 5 kN still considered?Tq
If you're referring to the top most force, applied at D, that is NOT considered when writing a moment about D. Please carefully look at the color coded boxes and lines, each corresponding to which moment is being calculated. The 5 kN used for the calculation is the one applied at point E.
@@QuestionSolutions ohh I see it now,my mistake.Thankyou
@@imansalim3874 Glad you got it :) Best wishes with your studies!
Hello, I would like to say that I am quite confused. can you tell me how do you determine if your direction of force is positive or negative?
The initial direction is just an assumption. If you get a positive value, then your assumption was correct. If you get a negative value, then it's opposite to your assumption.
In the problem 2, is it also same answer if i use the bottom part because i tried it and i got different answer or did i get wrong?
Regardless of where you start, you will always get the same answers. There is probably a numerical error in your solution or an error in setup of the equations. The forces in each member can't change based on where we start to solve the problem. :)
For the vertical truss, does that mean member BF doesn't need to be there since the force is 0?
In real life, no, because they are there to help with rigidity and stability. Sometimes, they will carry a force if the conditions of the bridge changes. lastly, they add to the aesthetics as well. People don't like seeing parts "missing" off of a bridge 😅
@@QuestionSolutions Hello! How come F bf is equal to 0 when the x component of Fbg is acting on BF and also 10 kN is also acting at BF?
I want a solution to find Fbf using moment method.
@@rpian1999 Please give me a timestamp so I know where to look, thanks!
@@QuestionSolutions 7:38 time in that video where Fbf is being determined.
@@rpian1999 So BF is a zero force member, that means it doesn't carry a force. The forces applied at B are carried by the other members, not BF. If you want, you can look at point B and do the equations, you will still get 0 for member BF.
I think sine is for summation of Fy and cosine is for Fx? Correct me if im wrong.
You are wrong, do not fall into that pitfall. I am not sure why students tend to this think way, but they are NOT related to Fy and Fx. It's all based on the side opposite to the angle. Please take a look at this video: ruclips.net/video/NrL5d-2CabQ/видео.html
Can you please enlighten me on why force BC and BG would be eliminated when taking the moment at B. I am confused.
Their lines of action go through point B. The same as the 5 kN force, and the y-component of force HG. If you need a refresh on lines of action, please kindly take a look at this video: ruclips.net/video/QNNnPZ68STI/видео.html
@@QuestionSolutions super helpful, thank you
8:42 i'm confused at this part. i thought sin DC should be eliminated because it will go thru pin H, and instead use cos DC? or does it depend on where the angle is placed?
So you have to always look at it from the perspective of the angle when doing trigonometry. Sine is going to give us the opposite side (opposite to the angle), which in this case would give us the x-component of force F_DC (horizontal line). That will create a moment since it's line of action doesn't go through point H. Cosine on the other hand will give us the adjacent component, (y-component, vertical line), which will go through point H, so it's eliminated.
@@QuestionSolutions ahh so we're getting the x component here but we just used sin because of the angle. I'm used seeing sin as y, and cos as x so i was confused😆. Thank u very much
@@armanjanndajab6334 Yes, but don't associate sin with x and cos with y. It's all based on the location of the angle. 👍 Best wishes with your studies
I confused in part 7:20 b/c the force BC=0 is it correct??what abt the external force 10kN
Sorry, I don't understand your question. We didn't calculate force BC? Did you give me the proper timestamp?
Regardless, all values shown are correct, except at 9:08, where force F_HI = 42.5 NOT 45.2.
In the first question can we use which equation we want? I mean when we use moment or Fx=0, Fy=0. We used only moment equation in this problem.
You can, but try to use ones that give you the answer the fastest.
@@QuestionSolutions okay thank you
I don't understand how do you know the direction of the force based of the positive/negative value? In the first example the value was positive 2 times in a row. In the first situation it was compression, in the second it was tension. How did you assumed those?
Please kindly watch this video first: ruclips.net/video/_rK02neOF18/видео.html Especially the introduction, where I explain how to determine whether things are in tension or compression. If, after you have watched it, and still have trouble, please let me know and I will do my best to help you out.
Thanks for the video, you explained this so well in a way my professor never could! 😭😭
Just a quick question though. At 6:16, you say that only the x-component of force BG creates a moment about point D but in the equation it says sin45.. I thought it would cos45 since it's the x-component. Can you please explain this part? It's the only thing I'm confused about
You're very welcome.
You have to make sure you look at the force from the angle. So if you were at the angle, and you looked from that perspective, the opposite side to the angle would be sine, which is the x-component, and the adjacent side is the y-component, which would be cosine. Or are you saying that sine is correlated with x-components and cosine with y-components? If so, this isn't true, please don't think that, it is completely incorrect. If you need a video on components with sine and cosine, please see this video, especially the first example: ruclips.net/video/NrL5d-2CabQ/видео.html
@@QuestionSolutions Omg I thought that x-components were always associated with cosine and that y-components were always associated with sine.. I'm going to check out the video that you linked, thank you so much!! 🙏🏽
@@joonfanatic2140 Thank you for asking this question. I was stumped for a while as well and also always assumed X was Cos and Y was Sin. Game changer for me!
@@AlexanderPerez-oe1gu Same here, it definitely changed my thought process and made me understand things correctly! I'm glad it helped you and hopefully you watched the other video he linked in the reply. I wish you the best in your studies 😄
@@joonfanatic2140 Thanks, yes I saw the referenced video, and totally made sense. Completely changed my perception of how to approach the x and Y components.
Really nice vedio
Sir I also want to learn such kind of annimation ....can you so please tell me
Or provide some vedio leink .I will be very thankful of you
I use aftereffects for animations. If you google or search on youtube "after effects tutorials" you can find lots :)
@@QuestionSolutions thanks you are great 👍
@@bashirullah4512 Thank you 👍
9:07 could you have used the moment at F and still got the same Force HI?
You can find the values using any moment location but try to use simple ones since you want to make your life as easy as possible. So go for the one that eliminates the most unknowns or leads to a direct force value.
Can you kindly explain why you used "sin" operation for x components and "cos" operations for y components....? i always thought we should use sin for y and cos for x...
Please see this video, it's less than 60 seconds: ruclips.net/user/shortsvynnKlJD_Jo?feature=share
Thank you so much
But there was a litt'l mistake in the 3rd problem; you use sine for the X components and cosine for the Y components
You are incorrect in thinking that sine is for x or sine is for y components or cos is for x components or y components. It doesn't work that way, and you are not alone, countless students make the same mistake on exams, and points get taken off. Please watch this video, it's less than 60 seconds and it will help you not make the same mistake I see so many students making. ruclips.net/user/shortsvynnKlJD_Jo?feature=share
3:46 PLZZ tell me how do you determine if its in cos or sin??? I understand the whole thing but always messed up the cos & sin part in the equation 😭😭
Please see: ruclips.net/user/shortsvynnKlJD_Jo?feature=share
I would really appreciate it if you could make a video about how to convert uniformly distributed loading on the truss to point loads. T-T
This might help: ruclips.net/video/lI5klge2GlM/видео.html
so every slope needs to represent vertical and horizontal components?
Sorry, I don't understand your question. What slopes?
how did you get FDE or FJI times by 3? why times by 3?
I don't know where you're referring to. Please use timestamps. Thanks!
Hi, can someone recommend a good software for creating 2D-sketches of such trusses?
These were drawn on illustrator but if you want to figure out the values in trusses after you input them into a software, you'd have to look for engineering software or construction software.
@@QuestionSolutions Wow, what a fast answer. Thank you very much, that's a good tip.
And btw.: Your videos are extremely helpful!
7:33
can you explain how ?
we have
3 other forces in the x direction
10 + 10 + 5 + BF = 0
BF = - 25
Where did you get those forces from? So when you look at a joint, you only look at that joint, you don't care about what happens at the next joint over. There are no other forces applied at joint F other than vertical forces. I think what you're doing is translating forces from other joints to this joint, but remember, when we look at a joint, it's isolated. That's why you draw a separate coordinate system about that joint. At 7:33, focus on the right side of the screen and look at the forces at that joint. :)
@@QuestionSolutions ❤
@@mastfamastfa1256 ❤
Can you please create a video for zero-force members
There isn't much to say about zero force members, or rather, I am unsure how to create a video on just that since it's a small section. I find that most students tend to realize on their own what zero force members are by doing a lot of questions. It's like an intuition that comes when you do a lot of the questions, you can just pick them out. Regardless, I will add it to my list of videos to do. Thank you for the idea.
first thank you very much for the incredible job.
But I got question! why didn't you give some 3d examples about this lesson (trusses)
You're very welcome. The reason is that usually, 3D examples aren't covered in first year courses. Maybe in the future, I'll make one :)
@@QuestionSolutions oh that's why. I'm studying at TuDelft university, we have to study everything also the friction, potential energy, virtual work, and centroid (this is for the first quarter in the first year). But lemme tell man, you did a great job I will do the resit and I am watching your videos they are very well explained, instead of looking at the lectures again and again. thanks man and happy new year.
@@anakhash190 Yeah, I think it depends on the university. Some of them are covered in 2nd year courses with a lot more in-depth details and questions than what the Hibbler book covers. Either way, I wish you the best with your studies. Keep up the great work :)
Can you do a video about space trusses?
I will add it to my list, but it probably won't get done for some time. I am still working on thermodynamics videos.
Glad I found these videos of yours. It was a very big help knowing I am having a hard time with our subjects right now because it was not explained properly but yours is very concised and well elaborated🤍
Glad it was helpful! I hope you do amazingly on your exams and I wish you the best ❤
How do you know when to take moment or Sum of forces in x,y to solve for unknown forces?
You usually have to do both methods to find all the unknowns. If you can find an unknown with a moment equation, then you should do that because it saves time. If you can't use a single moment equation to figure out a force, then you will have to sum forces in the x/y direction. This comes with intuition, so doing a lot of questions will help with this. I don't think there is a straight answer to your question. Try to do little as possible to get the answer to save time. That usually means starting off with a moment equation since you can eliminate a lot of the forces that go through the point where the moment is calculated.
@@QuestionSolutions how to determine which point to take to create moment eq ?
@@cokonkiyotPick a point that eliminates the most unknowns.
@@QuestionSolutions ahh i see . how to know which forces affect that moment ? i confuse lil bit even tho i watched ur video about it
Is force GH in compression or tension??
Please give a timestamp when asking a question. I am not sure where you're referring to. Thanks!
i dont get how to use cosine or sine. can you explain?
Please see: ruclips.net/user/shortsvynnKlJD_Jo
and
ruclips.net/video/NrL5d-2CabQ/видео.html
Does zero force members not apply when solving Method of Sections
It's not a matter of "applying" per say. You can find them when solving the whole truss or you can visually look for them too. It just depends on the truss given.
QUESTION : at 8:23 why didnt we divide height over base? Like 1.5/2???
Divide it by 2 to get the angle or to find what?
@@QuestionSolutionsdont we usually do Tan(angle)=(height/base) ??? Our height is 1.5 and the base is 2… why in the video we did the opposite…like base over height…sorry for my bad explanation
@@6rozh9 That's incorrect and you should remove that thought from your mind. Instead, remember, tan = opposite over adjacent. So you look from the perspective of the angle, and look for the opposite side to the angle. Here, that's 2 m, and the adjacent side is 1.5 m. While we are at it, remember this too. Sine is opposite over hypotenuse and cosine is adjacent over hypotenuse. Always look from the perspective of the angle and look to see what side is opposite to it and what side is adjacent to it.
@@QuestionSolutions I’ll memories it right now so it doesn’t get me confused…thank you soo much sir :)
@@6rozh9 Great! If you have any other questions, let me know. Keep up the good work and best wishes with your studies :)
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legend
Thanks!
Shouldn’t negative sign mean compression and positive sign mean tension?
Please see this video where I explain how to determine if a member is in tension or compression. ruclips.net/video/_rK02neOF18/видео.html
The negative sign indicates that your assumption for a force was incorrect, it's opposite to the direction you assumed.
Is FDC supposed to be 365.6 I'm confused on how you got 125
No, it's 125. Plug it directly as shown into your calculator and solve for F_DC. Not sure how you got 356.6, probably a numerical error. Also, for the future, please kindly use timestamps :)
VERY unimportant as it has no affect on the method but on 9:13 I think the answer is 42.5 not 45.2 but correct me if I am wrong
Yes, you are correct. There is a typo there. Good catch :)
6:23 why can't we take Moment about point C? I tried it and it doesnt work
You can take it about point C to figure out force BG, you will get the same answer. Most likely, you are making a numerical error or you're not accounting for the proper distances/forces. It's hard for me to say without seeing your steps.
@@QuestionSolutions it was a calculator error thanks
When are you starting with fluid mechanics
Not sure, probably not for some time. I have to finish thermodynamics first.
I believe there is a mistake at 9:07 . Solving for HI should be 42.5, not 45.2. lmk if I am wrong but I do not believe so.
Yeah, it's a typo 👍
I have one question of truss is there anyway to send you that question ?
I don't really solve problems because then I have to do everyone's questions and it takes too long, sorry 😅
@@QuestionSolutions yeah I can understand don't be sorry
@@saiprasadsatya3677 Thank you for being understanding. I appreciate it!