A uniform metre rule of mass 200g is pivoted at 0cm mark. Calculate the force which would be applied vertically up at the 60cm mark to keep the rule horizontal

There are two forces acting on the ruler: weight pulling down halfway at the 50cm mark, and the upward force at the 60cm mark.

Sum of the moments about the pivot:

∑τ = Iα

F (0.60) - (0.200) (9.8) (0.50) = 0

F = 1.63 N