What are common problems encountered when using a double pulley system?

[nu_hash]

Homework Statement

https://docs.google.com/file/d/0B65UbG8T0LS9SEFRTHhHZmR2NDA/edit
Question 2

Homework Equations

The Attempt at a Solution

Well I tried to draw a diagram but I don't really know where to start tbh, I also can't my head around how 1200N of force only provides 600N worthof acceleration

 

[Flipmeister]

Your link is inaccessible. You have to change the settings for the file so it can be seen publicly.

 

[nu_hash]

Sorry I fixed it now

 

[Flipmeister]

For starters, the lower pulley 'splits' the force the platform is pulling down with. Also, the drum is pulling on both the cable and the platform it's connected to.

 

[nu_hash]

This is what I have so far although it still seems wrong
http://db.tt/5P6gHmnn

 

[Flipmeister]

The values 1.8kN and 1.2kN are spot on. I don't know where you got 0.9kN and 2.1kN, though. The tension 1.2kN from the drum should cause a chain of action-reaction pairs along every segment of rope.

 

[nu_hash]

I see what I did wrong now, thanks for the help