Find mass using Torque?

Question

A uniform meter stick of mass M has an empty paint can of mass m hanging from one end. The meter stick and the can balance at a point 21.5 cm from the end of the stick where the can is attached. When the balanced stick-can system is suspended from a scale, the reading on the scale is 2.40 N. Calculate the mass of the meter stick.

Answer 1

Let:
m1- mass of the meter stick
m - is the mass in question

Summation of forces=0 or

Ft= (m1+m)g

Summation of moments = 0 or

Rmg=R1m1g
__________________

m1=Rm/R1
Ft= (m1+m)g
Ft=2.4=(R m/R1+ m)g since R1= .5 (center of mass) and R=.215m we have
2.4=(0.215 m/0.5+ m)g

m= (2.4/g)/(0.43)=0.569 kg