Question

A meter stick is found to balance at the 49.7-cm mark when placed on a fulcrum. When a 41.0-gram mass is attached at the 23.0-cm mark, the fulcrum must be moved to the 39.2-cm mark for balance. What is the mass of the meter stick?

Answer 1

Answer:

mass of the meter stick=0.063 kg

or

mass of the meter stick=63.3 g

Explanation:

Given data

m₁=41.0g=0.041kg

r₁=(39.2 - 23)cm

r₂=(49.7 - 39.2)cm

g=9.8 m/s²

To find

m₂(mass of the meter stick)

Solution

The clockwise and counter-clockwise torques must be equal if the meter stick   is in rotational equilibrium

$Torque_{cw}=Torque_{cw}\\F_{1}r_{1}=F_{2}r_{2}\\ m_{1}gr_{1}=m_{2}gr_{2}\\(0.041kg)(9.8m/s^{2} )(0.392m-0.23m)=m_{2}(9.8m/s^{2})(0.497m-0.392m)\\0.0651N.m=1.029m_{2}\\m_{2}=0.063 kg\\or\\m_{2}=63.3g$