A metre stick is balanced on a knife edge at its centre. When two coins, each of mass 5g are put one on top of the other at the 12cm mark, the stick is found to be balanced at 45cm. The mass of the metre stick is?

Question: A metre stick is balanced on a knife edge at its centre. When two coins, each of mass 5g are put one on top of the other at the 12cm mark, the stick is found to be balanced at 45cm. The mass of the metre stick is?

Let m be the mass of the metre stick concentrated at C, the 50cm mark as shown in the figure.

image

In equilibrium, taking moments of forces about C 

 , we get

10g(45−12)=mg(50−45);

10g×33=mg×5

m= 

(10×33)/5

​

 =66g