Momentums, Ladder against a wall force

[Mukilab]

Homework Statement

http://www.physics.ox.ac.uk/olympiad/Downloads/PastPapers/BPhO_PC_2008_QP.pdf

Question 6

Homework Equations

Moment = Force * Distance moved

The Attempt at a Solution

I have tried this and I am sorry to say that I have no idea how to work it out. I think it is something to do with moments but the centre of gravity is not about a pivot so I don't if I should still reference Y from W. Furthermore, since the exact location of W is not known, I can't just use pythagoras to find the distance of Y from W.

Any help would be great, thank you very much.

 

[tiny-tim]

Hi Mukilab!

I think it is something to do with moments but the centre of gravity is not about a pivot so I don't if I should still reference Y from W.

uhh? The question tells you to take moments about Y.

Get on with it!

Furthermore, since the exact location of W is not known, I can't just use pythagoras to find the distance of Y from W.

Read the question … it's a "uniform ladder", meaning that it's the same all the way along …

so W will be in the middle! ​