Question

A uniform metre scale balances horizontally on a knife edge placed at $55cm$ mark. When a mass of $25g$ is supported from one end, then the mass of the scale is :

• A. $200g$
• B. $225g$
• C. $350g$
• D. $275g$

Answer 1

The correct option is B $225g$

The centre of gravity of a meter scale will be acting at the mid point (50 cm) of the scale.

For the balance, the moment of forces on both sides of knife edge will be equal.

So, $mg\times (55-50)=25g\times (100-55)$ or $m=225gram$