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# M2 Lamina and Hanging Problem watch

1. Hello, I have a quick question about hanging problems involving Laminas.
Generally I can do the question were I have find the angle between and edge and a vertical.
The only problem is, I find it hard to identify the correct angle they are asking for.
For example on Question 4 on this paper
http://store.aqa.org.uk/qual/gceasa/...W-QP-JAN07.PDF

My teacher wasn't very helpful in explaining why it was the 63 degree angle and not the 27 degree one. I drew my triangle such that tan(x)=0.5

thanks
2. "find the angle between the edge AB and the vertical" - doesn't this explain it!? You have to make sure you've drawn the diagram right I guess...
EDIT: oh, I see why you're confused, the line AB goes through the pivot point. Ummm... just make it clear in your answer which angle you have calculated, for example by drawing a diagram. It wouldn't hurt to calculate the other angle too, just in case.
3. I struggle to see the problem too as it seems clear in the question

4. (Original post by TenOfThem)
I struggle to see the problem too as it seems clear in the question

Okay, give me a sec.
5. (Original post by TenOfThem)
I struggle to see the problem too as it seems clear in the question

here you go, so the question is why the angle labelled phi and not the one theta. As far as I can see they are both vertical. At this point im not even sure i know what the phrase means
thanks
Attached Images

6. (Original post by dragonkeeper999)
"find the angle between the edge AB and the vertical" - doesn't this explain it!? You have to make sure you've drawn the diagram right I guess...
EDIT: oh, I see why you're confused, the line AB goes through the pivot point. Ummm... just make it clear in your answer which angle you have calculated, for example by drawing a diagram. It wouldn't hurt to calculate the other angle too, just in case.
if I have both angles and write I dont know what exactly the question is asking for in terms of the angle (which vertical exactly xD). Would they mark both answers?
7. (Original post by jarasta)
here you go, so the question is why the angle labelled phi and not the one theta. As far as I can see they are both vertical. At this point im not even sure i know what the phrase means
thanks
Ah

A complete lack of understanding

The point of the CoM is that it will be directly below the point of suspension

So the line from x through the CoM is vertical
8. (Original post by jarasta)
if I have both angles and write I dont know what exactly the question is asking for in terms of the angle (which vertical exactly xD). Would they mark both answers?
No
9. (Original post by TenOfThem)
Ah

A complete lack of understanding

The point of the CoM is that it will be directly below the point of suspension

So the line from x through the CoM is vertical
Aaaahhh thats what the vertical is! This is news to me, good news. Yeah that makes perfect sense now , Thank you, :').
Another question, whilst you are here.
When it asks, the angle between AB and the horizontal, which side do you take to be the horizontal. In either question 4 on this paper (http://store.aqa.org.uk/qual/gce/pdf...W-QP-JAN11.PDF) or the question i've already posted
10. Does not matter angle is the same
11. (Original post by TenOfThem)
Does not matter angle is the same
aaah thank you for very much. I cant thank you enough
12. (Original post by jarasta)
aaah thank you for very much. I cant thank you enough
Np

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