Question

A uniform half metre rule of mass ‘m’ is pivoted at 30cm mark. When a weight of 60gf is suspended from one end

of the ruler, it is found to become horizontal. Calculate the mass of the ruler.​

Answer 1

Explanation:

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