Circular Motion Q (1 Viewer)

[BillyMak]

I've been doing a few questions on circular motion and a common part of a question is to find the centripetal acceleration of a point.

How do you do this? Surely it isn't as easy as saying
Centripetal acceleration=(v^2)/r=(w^2).r and subbing in the values for w and r?

 

[mervvyn]

It depends... in my trial we had to find the centripetal and tangential acceleration on a particle in uniform circular motion. For 4 marks, we had to derive it from scratch, which meant breaking down each of the vectors into xsin@ and so on, except x with two dots rather than just x.
Once you have expressions for each, you also need to differentiate the equation of the circle to take x = rsin@ and y = rcos@ into expressions involving x and y double dot, then subs and eventually it comes out = it's a bit less than half a page of working, but my maths teacher says you never know when you might get asked it in the hsc.
If you want, i can scan the proof (probably found in any good textbook) tomorrow and post it.

Edit: if you're not asked to find those accelerations, you may be able to get away with just quoting the formulae - other opinions?

 

[BillyMak]

I should really look at some textbooks.

I was away the day we covered it in class you see...

Thanks for the help though, I'll look into it.