Question

a uniform meter rule balances horizontally on a knife edge placed at 58cm mark when a weight of 20 gf is suspended from one end.What is the weight of the rule.

Answer 1

Let, W be the mass of uniform scale,
When the edge is placed at 58 cm mark and 20 g weight suspended at one end, then uniform scale would be balaced.

Applying here the principle of moments:

The uniform scale weight would be balanced at mid point i.e. 50 cm of the scale.
A weight of 20 g is placed at 58 cm mark.

So the clockwise moment due to mass of the scale will be W(50-42) = 8W

The anticlockwise moment due to mass 20g will be 20*(50-8) = 840.

For equilibrium, clockwise moment = anticlockwise moment

So, 

W x 8 = 840
W = 105 g 

The wight of the uniform meter = 105 g.

Answer 2

Answer:

This is the answer to the question