Edexcel M2/M3 June 6th/10th 2013

Can anyone tell me the all of the assumptions I.e. what rod, plank, particle, lamina mean (and any others)

Well you could determine them like this:
Keep you index finger at the point around which you are taking moments, then without moving it swing you thumb over and in the direction of the arrow of the force. After you have passed the arrow head see how best it can make a circle around that point. That circle will show if it is clockwise or anticlockwise.

You can use either the thumb or the index finger for either. What's seems more comfortable...

have you done a triangle thing for A to work out the vertical distance it moved? then just compare GPE

Take that for just an example, could you tell me what's clockwise and anticlockwise say about B?

Oops, my bad. :P

Could you help in the basic idea of toppling? What do we need to know?

Take that for just an example, could you tell me what's clockwise and anticlockwise say about B?

Clockwise would be F and R. W is anticlockwise

Clockwise would be F and R. W is anticlockwise

Do you have the orange and purple book?

No, F would not create any moment about B as it acts through the point. Just R and W would create a moment.

How do you do F? W and R are okay

No, F would not create any moment about B as it acts through the point. Just R and W would create a moment.

Are you sure? ;o can't we resolve F or something?

I am sure! A moment is given by F*d; where d is the shortest distance from the line that the force acts through, to the point we're taking moments about. As F acts directly through the point there is no moment as d = 0.

You could think about it in a number of ways: it is acting neither clockwise nor anticlockwise around B so how could a moment be created?!

Can anyone help me with how you do question 5 january 2006, finding the centre of mass of a a triangle WITHOUT THE LAMINA

Yes! What page?

56

Even if you've figured out that angle question, can you tell me where it's from so I can see if I can do it?

So thats part (a) right? How stuck are you? Do you know where to begin?