Question

a meter stick is balanced on a knife edge at its center. when two coins , each of mass 5 g are put one on of the other at the 12 cm mark, the stick is to balanced at 45 cm . the mass of the meter stick is

• A. 56 g
• B. 66 g
• C. 76 g
• D. 36 g

Answer 1

The correct option is B 66 g

$\begin{array}{c}\text{Correct option as}\left(B\right)\\ \text{For balanced at}45cm;T_{\text{net}}=0\\ \text{SO, Tork}=0\\ \begin{array}{cc}\overrightarrow{\gamma }\times \overrightarrow{F}& =0\\ -\mathrm{Mg}\times \left(5cm\right)+& \mathrm{mg}(45-12)+\mathrm{mg}(45-2)=0\\ M\times 5=& 5(45-12)+5(45-2)\\ M& =36g\end{array}+33\\ M=66g\end{array}$