🔺11 - Moment of a Force about a Point 2D Examples 1 - 3

[@hannahs.opigan7475]

Thank you so much! This is a great help for me!😭❤️

[@SkanCityAcademy_SirJohn]

Most welcome. Which school do you attend?

[@appledestroyer6513]

It is a very good video, very concise and informative. Most importantly, it is reliable.

[@SkanCityAcademy_SirJohn]

Aww thanks so so much. Where do you watch me from please?

[@jpg-g6i]

@@SkanCityAcademy_SirJohn I am watching from Australia much appreciated for the help

[@samarbader2761]

Absolutely amazing, I hope get 100 in this course

[@SkanCityAcademy_SirJohn]

Thanks so so much

[@NANOR_OB]

Thank you for this one ...I'm gonna ace this midsem 🔥🔥🔥🔥

[@SkanCityAcademy_SirJohn]

Good....

[@hbasyraff7973]

anti-clockwise shoould be positive right?if i'm not mistaken

[@SkanCityAcademy_SirJohn]

Its not fixed that anti-clockwise should be positive. You need to decide what you want to use and use apply. But if the resultant is negative it means the moment is taken in the opposite direction. Note, the resultant moment will always be same, changes will only be with regards to the direction

[@hbasyraff7973]

@@SkanCityAcademy_SirJohn thanks for that explaination

[@SkanCityAcademy_SirJohn]

Youre welcome

[@arinzeanthony7447]

@@SkanCityAcademy_SirJohn Thanks a lot for this, the sign convention is confusing.

[@SkanCityAcademy_SirJohn]

@@arinzeanthony7447 you are most welcome

[@user-wi8kg7yl5x]

Thank you so much this video made huge difference , however id like to know whether we should consider the signs when finding the components of each fore eg for the last question we solved , why wasnt the F2y component -519.62 , or do we just ignore the directions since we are working with moments ????

[@SkanCityAcademy_SirJohn]

Yes we don't consider it when finding the force components. It's rather done when finding the moment about the point.

[@SaddySimwinga-rn4vj]

Thanks 👍 so much... I have enjoyed it🎉🎉

[@SkanCityAcademy_SirJohn]

You are most welcome

[@rolandcoclet722]

good morning sir i was just wondering about signs of the moment, my teacher told me clockwise is negative but right now i m confused i would like to know if there is some exception or something like that . thank you and have a nice day.

[@SkanCityAcademy_SirJohn]

do not be confused about it. Clockwise can be negative or positive, either ways is correct. The issue is just choose a conversion for clockwise, ie if you take it to be negative, use that conversion throughout your solution, at the end if i use positive, our magnitude(answer) will be the same but different signs (- or +) If you have a negative resultant, it means the moment is rather in the opposite direction.

[@samahazard1491]

Wawooo ❤ explanation is clear here, hope everybody could explain like u

[@SkanCityAcademy_SirJohn]

Aww

[@user-gv5dd3bi5l]

Thank you. Very understandable

[@SkanCityAcademy_SirJohn]

You are most welcome

[@user-et5xw3dq1p]

Well done sir. However for question 2 am wondering why the 500N isn’t sin45 when finding the distance, because it would be opposite to the angle and cos45 for 300N

[@SkanCityAcademy_SirJohn]

Did you move the 45 degrees from the reference angle to the other side. If you did, then you will have opposite of mine. But if it remains at where it has been placed in the question, then you have to get what I got.

[@mgbelejohnboscochidera4553]

Nice one sir

[@SkanCityAcademy_SirJohn]

thanks so much. please where do you watch me from?

[@abdallehassan3597]

Thank you so much

[@SkanCityAcademy_SirJohn]

You are welcome

[@joelnamabwaza3896]

Thank you sir

[@SkanCityAcademy_SirJohn]

You are most welcome

[@mikumatt]

For #2, the Key in the book says 1.25 kNm, but I believe that’s because anti clockwise is suppose to be positive and clockwise is negative. Nevertheless helpful guide.

[@SkanCityAcademy_SirJohn]

The magnitude is what matters, as for the direction, it's on your preference

[@sunusimuhammad9227]

Thank alot

[@SkanCityAcademy_SirJohn]

You are welcome

[@FatawYakubu-908]

Please does it mean that for the upward force the direction is anti clockwise and for the downward force the direction is clockwise

[@SkanCityAcademy_SirJohn]

Not necessarily, it depends on the point you are taking the moment about and also where the perpendicular distance falls, whether left or right

[@FatawYakubu-908]

Okay thanks 🙏

[@SkanCityAcademy_SirJohn]

@FatawYakubu-908 most welcme

[@vicky3156]

Hello, please how do u know whether the direction for the forces should be clockwise or anticlockwise

[@SkanCityAcademy_SirJohn]

You need to made items to take the moment, force and perpendicular distance, so the force and where you have the perpendicular distance away from the line of action of the force determines the direction you must take.

[@Hola-tx9fr]

Hi teacher, thank you so much for your efforts. I just want to understand why in the second exercise, we did not project the forces onto the x and y axes like we did in the first and last examples.

[@SkanCityAcademy_SirJohn]

Aww, thanks so much for the words of encouragement, the reason why q2 looked different was that, the forces given were originally along either the x or y axes, so that makes it easy to just continue with the solution process, but for q1 and 3, the forces are at an angle with the x or y axes, meaning that that force is the resultant force having x and y components, hence we need to resolve in x and y before we continue with the solution

[@Hola-tx9fr]

​@@SkanCityAcademy_SirJohn ok. Thank you teacher 😊

[@SkanCityAcademy_SirJohn]

You are most welcome. Thanks for watching

[@magdalenapovanhu1478]

How do you know if the force is in the clockwise or anti clockwise moment??

[@SkanCityAcademy_SirJohn]

So first you note the point you need to take the moment about, next moment is force * perpendicular distance away from the point you are taking the moment about, so that will let you know if you will take it in the clockwise or anti clockwise direction.

[@keptstudioL]

please explain why you say that F1x corresponds with 4 and F1 corresponds with 5.

[@SkanCityAcademy_SirJohn]

This is because, F1x is parallel to 4, and F1 is also parallel to 5.

[@MemorizeQuranEasy]

Thanks for your good 🙏

[@SkanCityAcademy_SirJohn]

Youre welcome

[@zubairiacademy]

Assalam ala almushahideen almuslimeen Keif 7alkum

[@michaelasilidjoe4862]

From the last eg. I didn't understand why you multiplied the f1x by 0.25

[@SkanCityAcademy_SirJohn]

tracing the line of action of F1x to the left, you can see it cuts the line passing through O, the perpendicular distance away from O is 0.25m

[@michaelasilidjoe4862]

@@SkanCityAcademy_SirJohn Oh okay Thank you very much......

[@SkanCityAcademy_SirJohn]

@@michaelasilidjoe4862 you are welcome.. thanks for watching

[@kiarancl]

may i ask from what book are the examples from?

[@SkanCityAcademy_SirJohn]

Hibbeler statics

[@kiarancl]

@@SkanCityAcademy_SirJohn thank you! Great teaching

[@SkanCityAcademy_SirJohn]

Thank you very much

[@ndzitsakile]

On the second example why is the 300N acting in an anticlockwise direction and the 500N in the clockwise direction?

[@SkanCityAcademy_SirJohn]

no, its the other way round, check again and come back with your question. Thank you

[@ndzitsakile]

@@SkanCityAcademy_SirJohn what I want to understand is that how do we know if it's clockwise or anticlockwise

[@SkanCityAcademy_SirJohn]

So you just need to trace the line of action of the force, to cut or intersect the line of action of the point you want to take the moment about. Once you have the two, the moment will be the force x the perpendicular distance

[@ioriyagami8494]

Hey sir Good afternoon do you have some videos related to this?

[@SkanCityAcademy_SirJohn]

Yes please, kindly check the playlist on basic mechanics if what you want is part of the list.

[@ztrdyydjfufyfud4895]

first you took the force negative while its approving the ccw assumption that you made then you took fy with cosine while its clearly sin

[@SkanCityAcademy_SirJohn]

Kindly specify the question number so I clarify for you

[@AnnahtuDauda-gk9xr]

Ur diagram is always not clear how will we see the readings

[@SkanCityAcademy_SirJohn]

It's due to your data rate, try to select a high resolution on KZbin to see it clearly

[@hashiraarts285]

In ex. 3, why f2x=300N rotation is clockwise pls help

[@SkanCityAcademy_SirJohn]

Yes, it's has same direction as F1x, now the line of action of F2x if extended backward to he left is perpendicular to O. And you can only do that if you rotate in the clockwise direction

[@martinLmaina]

I think clockwise moment should be negative

[@SkanCityAcademy_SirJohn]

well you shouldnt think that, you can either choose clockwise moment to be negative or positive, the only thing is at the end the resultant moment should be the same, and the sign (whether + or -) indicates the direction of the resultant moment.

[@user-gv6jm9yb9s]

Pls why did you take Fx in the anticlockwise direction

[@SkanCityAcademy_SirJohn]

Please kindly start the time in the video or question number for easy reference

[@danialexquande7813]

How come 2.5sin45 become 1.7 something while mine get 2.13

[@SkanCityAcademy_SirJohn]

It's simply because your calculator is in the radian mode, kindly put in the degree mode

[@FatawYakubu-908]

Please why did you not multiply the f3y by the distance 5m

[@SkanCityAcademy_SirJohn]

For which question please, and can you state the exact time in the video?

[@FatawYakubu-908]

First example 6mns 55sc

[@SkanCityAcademy_SirJohn]

@FatawYakubu-908 it's because the force f3, does not end on the 5m mark, we defined the distance from o to the force as a which is less than the d = 5

[@FatawYakubu-908]

@@SkanCityAcademy_SirJohn okay thanks

[@ayamwenzdayz3551]

i think everyone here is used to clo0ckwise being negative so its kinda confusing

[@SkanCityAcademy_SirJohn]

Oh okay. I get it now. It's can be this or the other way round

[@nanaboakyeanthony1696]

When resolving the F2, why didn't you take the angle from the positive x axis?

[@SkanCityAcademy_SirJohn]

Kindly state for which question.

[@nanaboakyeanthony1696]

@@SkanCityAcademy_SirJohn The last question

[@SkanCityAcademy_SirJohn]

its actually the same thing, cos 60 = cos 300 = 0.5, looking at the direction where the force acts, the angle between the horizontal axis and the force is 60, hence its best to use that instead of going round in the anti-clockwise getting 300 degrees

[@nanaboakyeanthony1696]

@@SkanCityAcademy_SirJohn Alright. Thanks

[@SkanCityAcademy_SirJohn]

You are welcome

[@mostafasadeq3153]

My Thanks

[@SkanCityAcademy_SirJohn]

are you an egyptian?

[@mostafasadeq3153]

@@SkanCityAcademy_SirJohn yeah , I'm an Egyptian

[@SkanCityAcademy_SirJohn]

Okay. Kindly message me on [phone] on WhatsApp.

[@zubairiacademy]

@@mostafasadeq3153 izayak ya basha inta amil eh

[@zubairiacademy]

@@mostafasadeq3153 sallim li 3la ahl misr

[@abdallahally2863]

how anticlockwise is being 2 be negative

[@SkanCityAcademy_SirJohn]

It's not a standard. You just decide on your own which rotation should be positive or negative. I usually choose clockwise as positive and anti-clockwise as negative. You can do the opposite but in your final answer we should know the actual direction.

[@realhappenings2433]

Please why was the distance about O of the 300N that

[@SkanCityAcademy_SirJohn]

For which question??

[@dimospeaker6266]

it should not be +10kN? just wanna make sure

[@SkanCityAcademy_SirJohn]

Which question?

[@user-tm8nu6ms2y]

please i want to know if Ib=newton

[@SkanCityAcademy_SirJohn]

No, please. I changed from Ib to Newtons because we are mostly familiar with Newtons.

[@moviereviews1915]

Can i get your email

[@SkanCityAcademy_SirJohn]

[e-mail]

[@ukwenyabenedict5428]

You didn’t really explain this anticlock wise and clockwise stuff🥲

[@SkanCityAcademy_SirJohn]

Really....

[@hemmarajkanesan6881]

@@SkanCityAcademy_SirJohn sir can you do a separate video explaining clockwise and anticlockwise stuff please :) i still always get confused with that.

[@SkanCityAcademy_SirJohn]

@hemmarajkanesan6881 really, I will consider that, okay.

[@hemmarajkanesan6881]

@@SkanCityAcademy_SirJohn thanks a lot sir. this really means a lot

[@prayanprabhakar1013]

Thanks so much sir

[@SkanCityAcademy_SirJohn]

You are most welcome