Re: how do you measure mechanical advantage without using a Newton scale?

Hello Sam

mechanical advantage is the force amplifying effect of a simple machine 
(wheel, inclined plane, pulley system, or jack screw) Mechanical advantage 
is simply the ratio of the force applied to the force doing the work. 

For example, say you have a 100 pound rock that you need to move and you 
want to use a lever to do it. You have a five foot long board and another 
smaller rock to use as a fulcrum ( the pivot point for the lever).  If you 
place the fulcrum so that it is 1 foot away from the 100 pound rock, you 
will have four feet left to push against.  You could say that the 
mechanical advantage of this system is four because you have 4 feet to 
push on versus 1 foot to lift with.  With a 4 to 1 mechanical advantage, 
it would take a 25 pound force to lift the 100 pound rock.  In this 
system, the mechanical advantage is determined by the location of the 
fulcrum or pivot point.  If the fulcrum were located 2 feet from the 100 
pound rock, it would take roughly 67 pounds to lift the 100 pound rock and 
your mechanical advantage would be 3:2 , or 100 lb/67 lb, or 1.5.

I'm not exactly sure what you mean by Newton scale. If you mean a scale 
that reads in Newtons instead of pounds, it is easy to convert pounds 
force to newtons and vice versa.  There are 4.448 newtons in one pound 
force and 3.571 ounces in one newton.

I hope this has been helpful.

Good Luck 
Greg