M2 help pls

Part a answer is 3cm. Can anyone help with part b? Thanks a lot. I’ve worked out the distance from G to DC

Can you please post what you've done so far? You should have a diagram showing where the centre of mass must be if AB is inclined at 25 degrees. Let us know if you don't understand this part.

What I get is the center of mass(G) from AB=3cm, and tan25=3/AN, therefore DN(Distance from G to DC)=6-3/tan25. And then I’m stuck

What I get is the center of mass(G) from AB=3cm, and tan25=3/AN, therefore DN(Distance from G to DC)=6-3/tan25. And then I’m stuck

Forgive me for barging in, @Notnek , took me quite a while to edit this image and I just refreshed the page to see you've contributed awhile ago.



@Sherryew If you look at the diagram I have edited, this is how it would look like after the lamina has been suspended from $A$. All you do is rotate the image and align the Centre of Mass with the suspended point.

$\frac{3}{\tan(25)}$ will give you the distance of ${AK}$ from my diagram but you want the distance from the $DC$ plane to point $O$.

Think again, why is $6-\frac{3}{\tan(25)}$ wrong?

let F be the foot of the perpendicular from O to line AB.

the distance OF = 3

angle FAO = 25°

distance DA = 6

triangle AFO is right angled.

you need distance DF.

What is N? I can't see it mentioned in the question. Do you have a diagram?

Nah. Angle GAD=25, not FAO, and FO=2

Could you pls have a look at the diagram below by@ManLike007? N is the point K in his diagram

I don't know what you've tried but at some point you need to take moments in the y direction (looking at the original diagram).

So i.e. in part a) you took moments about AB. Go back to this original diagram and try taking moments about the horizontal that includes B. Remember that you now know this $\bar{y}$ from your working in b).

These international papers have some tough questions. The 2013 (R) had an even harder COM question than this one (question 6)

But unfortunately I’ve done that one correctly but couldn’t solve this one😭😭

Maybe this one is harder then The folded lamina was very unusual which is why I thought it was harder plus the working isn't easy either.

Sorry but I don’t know how to find the distance of O to the horizontal that includes B.

Maybe this one is harder then The folded lamina was very unusual which is why I thought it was harder plus the working isn't easy either.

Also came up in this year's M2 paper back in June, oh boy was I in for a treat when I thought it wouldn't come up.