Question

A uniform metre rule is balanced horizontally at 60 cm mark when a weight of 10 kg is suspended from one end. Draw labelled diagram for this arrangement and calculate the weight of the rule.​

Answer 1

Answer:

Let M gram be the mass of the rule. Since density of the rule is uniform, its weight Mg will act at its middle point i.e., at the 50 cm mark (Fig.).



The weight of the rule produces an anti-clockwise moment about the knife-edge O. In order to balance it, 10 gram mass is to be suspended at the end B, to produce a clockwise moment.

From the principle of moments,

Anti-clockwise moment = Clockwise moment

Mg × (60 – 50) = 10 g × (100-60)

or Mg × 10 = 10 g × 40

∴ M = 40 gram