In left drawing the hood sash is lowered most of the way.  In the right drawing it is raised most of the way.  It's not a light weight window, but slides easily if it's working correctly.

If we could see through to the back it would look something like these below. 

Red lines are the stranded cables which are attached to the sides and/or top of the sash, run across pulleys and are attached to the sash weight.  The sash weight is the counterweight which weighs almost as much as the hood sash and makes raising and lowering the sash a near-effortless operation.

If the cable on one side breaks (below), the hood sash might hang a little crooked.  It will definitely get harder to raise and lower.  PUT A SIGN ON IT and be very careful.  Do not raise or lower it until it has been fixed.

Repeat -- If there's reason to suspect that the cable on one side has broken, do not raise or lower the sash until it has been fixed.  CONTACT YOUR BUILDING DEPUTY ABOUT REPAIRS.

It's quite important to be very careful and not move the sash if a cable is worn, broken, or breaking.  In the 'half broken" state, the wear and tear on the unbroken cable will be extreme, increasing the chance that it will break too, and if it breaks, the sash comes down hard.

BY THE WAY if it comes down hard and hits power cords, it is likely that they will be ruined and should be replaced immediately.  Crushing of an electrical conductor changes its properties depending on the damage done and the change to its shape.  Fires start in cords like this.