Question

A metre scale is balanced on a knife edge at its centre. When two coins, each of mass 10 g are put one on the top of the other at the 10.0 cm mark the scale is found to be balanced at the 40.0 cm mark. The mass of the metre scale is found to be $x\times 10^{-2}$ kg. The value of x is _________.

Answer 1

Let mass of meter scale be m.
Balancing torque about knife edge

(0.02g)×(30×10−2)=mg×(10×10−2) m=0.06kg=6×10−2 kg