Question

A uniform metre scale is balanced at 20 cm mark, when a weight of 100 gf is suspended from one end. Where must the weight of 100 gf be suspended? Calculate the weight of the metre scale.

Answer 1

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

The weight of the scale acts on the right side of the 20 cm mark, so the 100 gf weight must be suspended on the left side, i.e. at the zero end.

Taking moments about 20 cm mark.

Moment in clockwise direction = W × 30 cm = 30 W cm

Moment in anticlockwise direction = 100 gf × 20 cm = 2000 gfcm

By the law of moments,

Moment in clockwise direction = Moment in anticlockwise direction.

30 W cm = 2000 gfcm

\[ \therefore \text{W} = \frac{2000}{30}\ \text{gf} \]

= 66.66 gf

Weight should be suspended from the zero end.