WAEC - Physics (2000 - No. 9)

A uniform metre rule of mass 90g is provided at the 40cm mark. If the rule is in equilibrium with an unknown mass m placed at the 10cm mark and a 72g mass at the 70cm mark, determine m
72g
102g
298g
504g

Explanation

Taking moment about the 40cm mark

Total clockwise moments = total anti-clockwise moment

m x 30 = 90 x 10 + 72 x 30

30m = 900 + 2160 = 3060

m = \(\frac{3060}{30}\) = 102g.

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