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
The correct answer is: B
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.