Question

A uniform half metre rule provoted at the 10cm mark balances horizontal when 150N is placed at the zero mark. Find thd mass of the half metre rule.

Answer 1

Answer:

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.