You are Here: Home >< Maths

M3 Statics of Rigid Bodies watch

Announcements
1. Attachment contains the question.

I needed some help in understanding how the triangle in the solution part has an angle of 20degrees. And also, how it was deduced that triangle OGS has an angle alpha on the dashed line produced by SG.

If anyone could offer further diagrams of how these angles were worked out it would GREATLY be appreciated.

Question and solution are in word attachment below.

MANY THANKS!
Attached Files
2. statics of rigid bodies.docx (155.0 KB, 79 views)
3. can anyone offer any advice please? mainly on the point of how alpha is placed on the right hand side triangle in the solutions.

Thanks!
4. (Original post by Dalek1099)
...
Hi, I've heard you are a somewhat of a genius at maths

Would you be able to shed some light on the solution provided in the first post please(its in the word attachment). Mainly on how they deduced triangle OGS has angle alpha on the dashed line SG produced.

Thanks
5. (Original post by Coral Reafs)
Hi, I've heard you are a somewhat of a genius at maths

Would you be able to shed some light on the solution provided in the first post please(its in the word attachment). Mainly on how they deduced triangle OGS has angle alpha on the dashed line SG produced.

Thanks
I Don't do M3 till next year sorry M2 is hard enough-the mock was so hard that I think my class are going to have another one.
6. (Original post by Dalek1099)
I Don't do M3 till next year sorry M2 is hard enough-the mock was so hard that I think my class are going to have another one.
ah ok, would you maybe know anybody else who can explain it?

thanks anyway
7. (Original post by Coral Reafs)
ah ok, would you maybe know anybody else who can explain it?

thanks anyway
This guy is virtually the god of maths:
http://www.thestudentroom.co.uk/member.php?u=937760
8. (Original post by DJMayes)
...
Hi, very sorry to bother you, but I'm stuck on understanding the method of a question.

The question and method are in the first post, in the word document attachment.
My confusion was, how in triangle OGS the dotted line produced by SG had an angle of alpha. I understand that alpha is the angle that the rectangular plane face makes with the horizontal, but I don't know how to put this to use.

9. (Original post by Coral Reafs)
Hi, very sorry to bother you, but I'm stuck on understanding the method of a question.

The question and method are in the first post, in the word document attachment.
My confusion was, how in triangle OGS the dotted line produced by SG had an angle of alpha. I understand that alpha is the angle that the rectangular plane face makes with the horizontal, but I don't know how to put this to use.

Firstly, note that the angle between the plane and the radius of the semicircle touching it is 90, as the plane is tangent to a circular arc. This allows you to deduce angle OGS as 20 degrees.

Now, you define alpha as the angle between your horizontal and the flat face of the semi-circular cross-section. Call the point from which you measure the angle as B. Then, OBSG is a quadrilateral, with angles BSG as 90 degrees (Obviously, as this is horizontal-vertical) and OBG 90 degrees (As the centre of mass of the object is in the middle by symmetry). Using the sum of the angles of a quadrilateral as 360, you deduce angle OGS as 180 - alpha, giving the angle you mentioned as alpha (Angles in a line).
10. (Original post by DJMayes)
Firstly, note that the angle between the plane and the radius of the semicircle touching it is 90, as the plane is tangent to a circular arc. This allows you to deduce angle OGS as 20 degrees.

Now, you define alpha as the angle between your horizontal and the flat face of the semi-circular cross-section. Call the point from which you measure the angle as B. Then, OBSG is a quadrilateral, with angles BSG as 90 degrees (Obviously, as this is horizontal-vertical) and OBG 90 degrees (As the centre of mass of the object is in the middle by symmetry). Using the sum of the angles of a quadrilateral as 360, you deduce angle OGS as 180 - alpha, giving the angle you mentioned as alpha (Angles in a line).
Thank you for taking the time to produce a very detailed post, this has helped me immensely and I can't thank you enough for responding this late at night too!!

very much appreciated and I gave you a +1

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: May 13, 2014
Today on TSR

Four simple steps to get an A*

Here's all you have to do

University open days

• University of East Anglia
All Departments Open 13:00-17:00. Find out more about our diverse range of subject areas and career progression in the Arts & Humanities, Social Sciences, Medicine & Health Sciences, and the Sciences. Postgraduate
Wed, 30 Jan '19
• Aston University
Wed, 30 Jan '19
• Solent University
Sat, 2 Feb '19
Poll
Useful resources

Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

How to use LaTex

Writing equations the easy way

Study habits of A* students

Top tips from students who have already aced their exams

Chat with other maths applicants