Why Does a Sliding Rod Lose Contact with the Wall at Two Thirds Its Height?

[gloacha]

Hi, somebody can helps me with this problem...

A uniform rod of length L supported on a wall starts to slide down without
friction. Show that the upper end of the rod loses contact with the wall when it is
found two thirds of its original height.

Thanks

 

[aniketp]

You have to find the andle which the rod makes withthe ground and prove its sine to be 2/3