torque
posted by sar .
A meterstick is found to balance at the 49.7 cm mark when placed on a fulcrum. When a 50.0g mass is attached at the 10.0cm mark, the fulcrum must be moved to the 39.2 cm mark for balance. What is the mass of the meterstick?
All of the problems ive been doing i needed to find length of meter stick, so I am not too sure on how to solve this. thanks

You know the length of the meter stick, one meter (100 cm).
First we need to find the center of gravity. We know that is at 49.7 am because that is where it balances all by itself.
now we put the 50 g mass on,
take moments about the 39.2 balance point.
50 (39.2  10) = m (49.739.2)
solve for m 
10.5