Question

A uniform metre rule balances on a knife edge at the 60cm mark when a weight of 20N is suspended at one end. Calculate the weight of the metre rule.

Answer 1

Let the weight of the metre rule be represented by W. Since the metre rule is balanced, the total clockwise moment about the knife edge is equal to the total anticlockwise moment.

Clockwise moment = 20N * 40cm = 800 Ncm
Anticlockwise moment = W * 60cm

By setting these two moments equal to each other, we can determine the weight of the metre rule:

800 = W * 60
W = 800/60
W = 13.33 N

Therefore, the weight of the metre rule is 13.33 N.