Question

A uniform meter scale can be balanced at the $70.0cm$ mark when a mass $0.05kg$ is hung from the $94.0cm$ mark. Find the mass of the metre scale :

• A. $6kg$
• B. $0.06kg$
• C. $0.07kg$
• D. $60kg$

Answer 1

The correct option is B $0.06kg$

As the scale is uniform, so the weight will be balanced at mid point i.e. 50 cm of the scale.

Let, $M$ be the mass of the meter scale.

Using principle of moments, for equilibrium, sum of moment of force on left side of knife edge is equal to sum of moment of force on right side.

So, $(70-50)Mg=(94-70)0.05g$ (as moment of force $=$ force $\times$ perpendicular distance from fulcrum)

or $M=0.06kg$