Applied Math Theorems

LilMissCiara

I only heard about there being a theorem on Q8 in the applied math exam, haven't seen or heard anything about them before...

Was wondering if anyone knows where I can get a copy of them.. The syllabus doesn't have them!

ride-the-spiral

There's the Perpendicular Axis Theorem and Parallel Axis Theorem. There are proofs for them in Fundamental Applied Maths, but I don't think they're ever actually examined.

LilMissCiara

ride-the-spiral wrote: »

There's the Perpendicular Axis Theorem and Parallel Axis Theorem. There are proofs for them in Fundamental Applied Maths, but I don't think they're ever actually examined.

They defo come up every year on Q8... There's 6 but in the past 10 years number 3 has come up once and and the other times it's been number 2 or 4.

ride-the-spiral

Well I know that the "Prove that the moment of inertia of..." comes up every year, but I've never seen the Parallel or Perpendicular Axis theorems be asked. In 2001 they asked to state them but nothing more.

The proofs over the last while have been moment of inertia of a uniform rod and disc, the most unusual one I've seen is 1995 it was a square lamina, and in 1998 they asked to prove the the kinetic energy of a rotating square lamina was (1/2)Iω^2. Not sure about the years before that though...

magicianz

For the a parts of Q8 it can be a rod, square lamina, hoop, disc, annulus or triangular lamina. Usually if its a square/triangle/annulus, then the shape would be used in the part b.

The parallel and perpendicular axis theorys are in your log tables under moments of inertia, if your asked to state them just put down the formula and label each term, include a diagram showing everything. =]

You should know them already, you need them both if you want to do Q8 at all

Bottleopener

Yeah, question 8 is surprisingly straightforward. If the part (b) looks doable, I plan on doing this question first in the exam as a bit of a nerve settler :P. The 20 marks for writing out a theorem is awesome!

http://thephysicsteacher.ie/appliedmathshome.html

This guy has them under his RBR section .

Maybe_Memories

As far as I can remember, the sphere was asked one year. Which was a bit daunting because most people were used to dealing with 2D shapes.

It was ages ago, and could possibly have been before 1977, which was the year the current syllabus came into use.

It would be pretty handy to know how to do it though - on my 2010 paper the Annulus came up for the first time since like 1987, I was so happy to see it

If anyone actually wants to know how to get the moment of inertia of the sphere, I can explain if you want.

magicianz

Im pretty sure in the current syllabus there is nothing 3 dimensional