How do restoring forces return a balanced beam to horizontal?

[kittu1421]

This has botherd me for quite sometime ...imagine a beam or a simple scale supported at its centre and carrying equal weights on two extreme positions on the scale from the centre, now under equilibrium the scale will be horizontal...now my question is if one of the weight is lowered by action of some external force, how does it come back to its horizonatal config. What and how are the restoring forces generated...??

 

[Hassan2]

A straight bar on a razor-edge pivot would not come back to its horizontal config but a slightly curved bar with its ends lower than the pivot would. I think you can figure out why.

 

[kittu1421]

gottcha...