Moment About a Specified Axis | Mechanics Statics | (Learn to Solve Any Question)
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- čas přidán 7. 08. 2024
- Learn to find the moment about a specific axis instead of a singular point. We talk about a scalar method and a vector method to solve these problems. We also go through 3 examples step by step.
In the examples, sometimes it's shown that a force would turn an object about a point or an axis, in reality, this is only to help students visualize the moment created by a force.
🔹 How to express forces with coordinate direction angles: • Addition of Cartesian ...
🔹 How to solve a triple scalar product (cross product): • How to Solve a Scalar ...
🔹 Moments of a force: • Moment of a Force | Me...
🔹 How to find position and unit vectors: • Force Vectors Along a ...
Intro (00:00)
Determine the magnitude of the moment produced by this force about the x axis. (02:48)
Determine the resultant moment (04:06)
Determine the moment of this force F about an axis (05:30)
Find more at www.questionsolutions.com
Book used: R. C. Hibbeler and K. B. Yap, Engineering Mechanics Statics.
Hoboken: Pearson, 2017.
Thank you so much with these videos. I am a first year and been struggling with Engineering Statics but your videos brought some light to my studies. I thank you a lot.
You're very welcome. I try my best to make them as simple and concise as possible. I hope your first year goes really well. Keep up the great work!
Me too bro
@@kagisojonathan4596 :)
Your explanations are brief yet so informative and comprehensive! Finally I feel like I'll be able to pass my statics course with decent marks:) Thanks a lot!
I am really glad to hear that. I hope these are really helpful to you, and I wish you the absolute best in your statics course :)
Thank you so much. This short video explained to me what multiple hours of lectures couldn't
I am really glad to hear that :) Keep up the good work!
Thank you, learned more from this video than a month of lectures.
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Your videos are so helpful, The way in which you make these videos helps me comprehend the topics very quickly. Your videos also help me bridge the gap between statics and calculus which in my opinion is very powerful. Thank you!!
I'm so glad! Thank you very much and I wish you the best with your studies.
Thank you for this video, it is easy to understand and very detailed. The way it is teached is not too fast and not too slow. Thanks a lot, I just hope I found this channel much earlier.❤
I’m so glad to hear that you found the video helpful and easy to understand! I try my best to provide content that is detailed yet accessible, and it’s wonderful to know that the pace worked well for you. Your kind words mean a lot! Best wishes with your studies :)
Great video, thank you so much! The visuals really help
I am really glad to hear that! Keep up the good work.
Love you, sir, I struggled with this but now I understand better.
Glad it helped! I wish you the best with your studies.
thank you thank you thank you, i just spend 4 going through the same content in the bookand still couldnt understand.4 hours !!!! and you just explained it to me
That's really awesome! Very happy to hear this was helpful. Keep up the good work and best wishes with your studies.
Thank u bro💓 u make sense and its very easy to understand
You're welcome bro ❤
Keep doing this work bro. Trust me you will gain much more subs and grow with time. like the sufficent engineer channel. He was just like you now he have 342k+ subs.
Thank you so much :) Really appreciate it!
Lol forgot this man earned a sub so bad I smashed that shit
Thankyou so much. It really helped👍
You're very welcome, I am glad to hear they helped.
Thank you so much, this is exactly what i needed ❤.
You're very welcome. I am glad the video was helpful and I wish you the best in your studies. Keep up the great work! ❤
you know you're doing a good job when you're video gets 0 dislikes. GOAT
😅 It's only a matter of time, someone will leave a dislike without explaining why, but I try my best :)
@@QuestionSolutions hey it’s like that in social media. Dislikes are bound to happen.
@@darrylcarter3691 That's very true!
Thank You for the great video to understand moments
You're very welcome!
Good video, thanks. This topic is hard to fully grasp, especially when the axis is 3D. Your videos makes it more comprehendible, especially when using the hibbeler books to study with them aside
Glad to hear. Keep up the great work and best wishes with your studies.
Thank you very much sir for explaining the concept so clearly. Although my teacher explained it very well, I did not focus and hence did not understand. But thanks to you I've caught up with the class.
You are most welcome! Keep up the great work and I wish you the best :)
Thank you so much sir it's really helpful 🙌🏽
You're very welcome!
bro u are really underated nice video
Thank you very much! 👍
Awesome videos man statics has so few resources, so your work is very precious to me thanks.
You're very welcome! I hope these videos help you out and I wish you the best with your studies. :)
Thank you soo much. 😍
You're very welcome!
wow, helped alot. thanks
Glad to hear!
Thank you so much
You're very welcome!
Thank you so much sir.
You're very welcome!
o thanks Allah iam lucky to watch ths before my final exam tomorrow of statics thanks my mate
😇
You're very welcome! Best wishes with your studies.
Could you please make videos on electrical engineering. Your videos on statics are so helpful!
Yes, it's on the top of my to-do list. I just need to finish the thermodynamics videos first.
you know about extra critic points which can make you better teacher than others.
Thanks!
THANK YOU SO MUCH
You're very welcome!
thank you
You're welcome.
thank you so so so much
You are very very very welcome!
Hey, I appreciate the helpful videos. I have been given a problem in my statics class in 3 dimensions, where I am provided with the moment about an axis and have to find the magnitude of the force that caused it. Any idea how I could do this?
So it's a matter of working backwards. Do you know the process to calculate the moment in a 3D problem if you're given a force? You take the cross product? If yes, you'd just have x,y,z variables for the force and you'd have numerical values for the moment. If you're unfamiliar, please see this video: czcams.com/video/QNNnPZ68STI/video.html
@@QuestionSolutions thanks, I got it eventually
Veryyy nice explanation
Thank you very much!
Thank you
You're very welcome!
For the last question, dont you have to multiply the last bit by Uac since u only found the magnitude of the moment and the question asks for the moment?
No, the cross product gives us a scalar moment value.
for my homeowrk, i'm getting 0 for the moment about an axis. What does this mean? what are the conditions that would result in a moment of 0 about an axis?
One scenario is when the force is parallel to the axis about which a moment is calculated. Please see: 1:20
Please for the last question if I made the position vector of AC 4i + 3j + 0k instead of Oi + Oj -2k would it work?
AC is already 4i + 3j + 0k, it's CB that's 0i+0j-2k. So I am unsure of your question. 🤔
@@QuestionSolutions I've got it now. Thank you so much. Your videos are very helpful.
Hello How did you calculate the position vector (rcb) in the last question. shouldn't be C: (0i,3j,0k ) and B: (0i,0j,-2k) ?
You really have to look carefully because a lot of students lose marks by skimming through the diagrams. Notice the 4m, which is along side the x-axis. That tells us that point C is 4m in the positive x-direction. Then look at the 3m, which is parallel to the y-axis. This tells us, point C is 3 m in the positive y-direction. It has no z-component. So your C point is incorrect because you didn't account for the x-axis.
B point is also incorrect. It's 4 m in the x-direction, 3 m in the y-direction and 2 m in the negative z-direction.
Always double check, it's super easy to lose marks at these points. I hope that helps :) If you need a refresh, see this video: czcams.com/video/CCeWy1kmxMs/video.html
2:57 for this question, how can i find the maximum moment produced by force F=450 N about x-axis of the pipe, what can i suggest to adjust any parameters to achieve the maximum moment?
The solution given is the maximum since we calculated it based on the whole force applied.
@@QuestionSolutions what should i answer when question asked ti suggest any suitable parameters that can be adjusted to achieve that max moment?
A larger force would increase the moment, a force applied direction perpendicular to the x-axis would increase the moment, a force applied further away from the x-axis would increase the moment, etc. @@nrulhikmh
Hii! I wanted to ask something about the vector F at 6:00. Why is it not the same as B (i.e. 4i +3j + -2k)? Are they supposed to be different?
The vector F, is actually just showing the force applied at B. It's the force written in cartesian form, which is why it was given with the letter F. A single point isn't a vector, so just B alone wouldn't be a vector, it would need to go from one point to another. I hope that makes sense? Let me know if you need more clarifications. :)
@@QuestionSolutions so if i use AB=(4i +3j + -2k) then it wont work?
@@dsking6975 The question is asking for the moment about AC axis, so you need a position vector from A to C.
4:03 I got the value of Mx as 42.9. Are you sure yours is correct? Maybe I made a mistake but I can't see where I've gone wrong...
Yes, the answer in the video is correct. I can't say where you went wrong without looking at your steps. I have a video on how to solve these step by step, please take a look: czcams.com/video/F8IHrg3pc7g/video.html
Best wishes with your studies.
thanks alot for this lovely video, jazaka Allahu khair, but can u pls tell me? I dont get how 2 find the unit vectors in 3:48
These are established. So you just need to remember them. The unit vector for x-axis is 1,0,0. For y-axis, it's 0,1,0 and for z-axis, its 0,0,1. The math behind it should be in your linear algebra book actually.
@@QuestionSolutions Thank you so much ☺️☺️☺️☺️
@@amrhelmy5795 You're very welcome!
6:27 i used rAB (4i+3j-2k) and rAC but become -14.4kNm
Also: 6:20 When using the uAB and rAB i become the same and this is much quicker, is this just coincidence because of the 12 and 24 that cancel each other or is this an actual shortcut?
uAB remains the same, only thing that changes would be rAB or rAC. If you got -14.4, then it's a numerical error, please double check if you did your negatives and positives correctly, and you should end up with the same answer.
I like this channel a lot honestly but i feel you could make stuff longer by putting steps for everything you do regardless of whether youve spoken on it before. Honestly, I love the channel though I dont feel there's a rush as to why its always 10 minutes max
I value your opinion, unfortunately, it's not one that's shared by a lot of people. It's too time consuming to go over the same steps over and over again, it's like explaining the Pythagorean theorem repeatedly. Instead, creating short videos that are concise is what people really enjoy. If you read the comments on most of these videos, students really value things that give the most information in the shortest amount of time. When you read your textbook, does chapter 3 go through the steps of chapter 2? No, it expects you to understand chapter 2 material and built upon on it. Does your professor cover the steps of chapter 1 when chapter 5 is being explained? Time is valuable, for the creator and for the viewer. It's hard to go through the same stuff over and over again because most students have already got it down by that point. Also the reality is, the majority of people prefer short concise videos. If you need to refresh on a previous topic, simple re-watch it, it's the best option. :) Thanks again for your input, but it's something that isn't feasible. Kindly re-watch any topic you don't understand. If the videos aren't helpful or too quick, there are a lot of other videos on CZcams that build on the same concepts so maybe a mix and match would help you better.
Is there an easy way to spot out the perpendicular distances...for some reason i cant seem to get it
I don't think there is, but something that might help you is to use actual real life objects, like erasers, boxes, etc and just get a feel for it.
I'm still a beginner on this subject, how did you get the Ux part?
Please give a timestamp so I know where you're referring to. Thanks!
For 1st problem we take unit vector as ux=1i+0j+0k but last problem why we need to take unit vector seperately?
In the first question, it's about the x axis, which has a unit vector of 1,0,0. So we don't need to calculate anything. For the last question, it's about the AC axis, for which, we do need to calculate the unit vector. For future reference, the unit vector for the y axis is 0,1,0 and for the z axis, it's 0,0,1.
6.27 from using a Mab i got 0.02. and u said only the middle row will change however isnt the Z for B -2k, which would mean both top and middle row will change. or am i missing something
The middle row will have 4,3,-2 since the position vector is the only thing that changes. I redid it to check with the new position vector, and I got the same answer, so I am unsure how you got the 0.02. What was the position vector you got for rAB?
@@QuestionSolutions for rAB i got 4i + 3j -2k and for my Uab i got 0.74i + 0.56j - 0.37k my magnitude is 5.38
@@edran4449 Your unit vector is incorrect. The unit vector doesn't change, it's based on the axis we take the moment about. So here, our axis is the AC axis, so our unit vector is UAC. That's why I said only the middle row changes, so only the position vector changes. 👍
@@QuestionSolutions oh ok thanks
@@edran4449 You're very welcome!
For the first question is it possible for me to -(450 cos60°) instead of 450 cos 120?
Yes, of course 👍
@@QuestionSolutions thank you
@@kellypatrick1473 You're very welcome.
1:20 The Force actually acts in an axis parallel to x-axis but the rotation of box is about z-axis not x-axis
I said "the box WON'T turn about the x-axis" 😅
when do you use vector analysis and when do u use scalar analysis :0
If you can solve the problem using scalar, use scalar, it's faster and easier. If you can't, use vectors.
How can I learn more about the right hand rule
I talk about it a bit on this video: czcams.com/video/QNNnPZ68STI/video.html
I want to ask in 5:45 you said that we can take postion vector from AB or CB both will work so ı take AB but it didnt work ı found 9.6 kN.m
Yes, absolutely. What was your position vector for AB?
@@QuestionSolutions 4i+3j-2k
@@sevgipnar5261 I get the same answer, please recheck your work. The only thing that changes is just the 2nd line in the matrix. So at 6:21, the second line should be 4,3,-2. Everything else remains the same.
@@QuestionSolutions yes ım doing the same matrix my matrix calculation is like this :
0.8 [ 3x(-3) - (-2x12) ] + 0.6 [ 4x(-3) - (-2x4) ] + 0 [ 4x12 - 3x4 ] = 9.6
@@sevgipnar5261 Your second step is incorrect. It should -0.6, not positive. It goes + - +. Please kindly see this video to see how to solve scalar triple products: czcams.com/video/F8IHrg3pc7g/video.html
Let me know if you need further help.
Hi, can you please do a video on "changing line of a force"?
I am not sure what you are referring to when you say changing line of a force. Can you elaborate please?
@@QuestionSolutions In statics, when you move a force to a different point not on its original line of action, the effect of this movement is represented by an equivalent force-couple system. So basically moving the force somewhere that is not along its line of action.
@@KeidenIsKayden I believe I have videos on that topic, though it's called something else. Please check the statics playlist.
@@QuestionSolutions Great, I will check now. Do you by any chance also have a video on finding where a resultant vector intersects a plane?
Hi
Sir, which software do you use for making videos?
After Effects to animate, Illustrator to draw the images.
@@QuestionSolutions thanks sir
@@saleemshahzad9697 You're very welcome!
@@QuestionSolutions Sir how can I connect with you? instead for youtube
@@saleemshahzad9697 contact @ questionsolutions .com without any spaces would work. If I reply, they sometimes go to junk/spam, so please check those as well.
So is this mixed triple product?
What do you mean by a mixed triple product? Where are you referring to?
In the first q why is it 450 cos 120 and not 450 cos 60?
Pls help me understand....
I actually explain it in the video, starting at 3:08. If you need a refresh on this topic, please watch this video, where I go through breaking forces into components, and explain in detail about the coordinate direction angles: czcams.com/video/mz7gPpIL0Gk/video.html
will make an assumption. At 6:23, where you got 14.4 kN • m, if wanted to find the moment(torque) in Cartesian Form, just take 14.4 kN • m and multiple it by the unit vector at AC.
Let me know the result you get with that method :)
@@QuestionSolutions {11.52i + 8.64j + 0k} kN • m
@@darrylcarter3691 If you take the magnitude of that, you will get 14.4 kN • m
@@darrylcarter3691 Hello darryl, how did you get this ? 14.4 multiply by what?
@@stijn1574 just multiply the unit vector of AC by 14.4
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why didnt you use triple product for 4:17
You can, you will need to express the force and a position vector from the axis of rotation to the force in cartesian form. Here, you can do it in scalar too since it's really easy and forces are all vertical or horizontal. So you can do it whichever way you like.
I love you
😅 Thanks!
For the last problem when solving for Rac I believe you swapped i and j components by mistake.
No, they are correct. The x-length is 4m and y-length is 3m. Unless this wasn't what you were referring to? Please give me a timestamp so I can check it again. Thanks!
Thank you for the fast reply. You are correct I realize my mistake now. Going to take my test now. Thank you for the help!
Please, I tried to use rAB and didn't get the same answer for the last question
I don't know what I'm doing wrong, @questionsolutions
What was your position vector from A to B?
Thank you so much
You're very welcome!