Question

5. A uniform half metre rule can be balanced a
upwards at the 100 cm mark.
29.0 cm mark when a mass 20 g is hung from its
end.
(a) Draw a diagram of the arrangement.
(b) Find the mass of the half metre rule.
(C) In which direction would the balancing pom
shift if 20 g mass is shifted inside from its one
end ?​

Answer 1

Let the weight of the half metre rule be x gf and it acts at the 25 cm mark (centre of gravity).

Now,

Acticlockwise moment = x×4

Clockwise moment = 20×21

In equilibrium,

Anticlockwise moment = Clockwise moment

4x=20×21

x=105 gf.

Thus, the weight of the metre rule is 105gf.

We know, one gf is the force acting on the body of mass 1 grams, thus mass of the body is 105grams.