The fulcrum is the point in any mechanical device where the moment due to weights is zero.
(Weight 1 x distance 1) - (weight 2 x distance 2) = 0
(1.7 Kg x 1.5 m ) - (weight 2 x 1.2 m) = 0
weight 2 = (1.7 Kg x 1.5 m ) / 1.2 m
= 2.1 Kg
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