Question

A uniform rule of weight $10$ gf us pivoted at its 0 marks.
(1) What moment of force depressed the rule?
(2) How can it be made horizontal by applying the least force?

Answer 1

Given that,

Weight $w=10gf$

(a). Moment of force = magnitude of force X perpendicular distance of the line of action of force from the axis of rotation

$=50cm\times 10gf$

$=500cmgf$

(b). To apply the least force we obviously have to make the perpendicular distance highest.

Hence, the least force should be applied at 100 cm mark

Thus, by principle of moments

$500gfcm=100cm\times F$

$F=5gf$

Hence, the force should be 5gf upwards at the $100cm$ mark