Question

A uniform metre scale balances horizontally on a knife edge placed at 55 cm mark, when a mass of 25 g is supported from one end. Draw the diagram of the arrangement. Calculate mass of the scale.

Answer 1

As metre scale is uniform, therefore its mass acts at 50 cm mark.

The 25 g mass is supported from the 100 cm end.

Taking moments about 55 cm mark.

Moment in clockwise direction = 25 g × 45 cm = 1125 g cm

Moment in anticlockwise direction = M × 5 cm = 5 M cm

By the law of moments,

Moment in clockwise direction = Moment in anticlockwise direction.

5 M cm = 1125 g cm

\[ \therefore \text{M} = \frac{1125}{5}\ \text{g} \]

= 225 g