Question Detail
Question
A uniform meter rule which has a mass of 75 g is suspended by a thread at the 75 cm mark and is balanced by a mass of weight W hanging from the 90 cm mark. Calculate the value of W in g.
Correct Answer
Option D is the correct answer.
Detailed Explanation
The meter rule weighs 75 g acting at its center (50 cm mark). Pivot at 75 cm. The distance from pivot to center of mass = 75 - 50 = 25 cm to the left, producing counterclockwise torque = 75g × 25. The weight W at 90 cm is 90 - 75 = 15 cm to the right, producing clockwise torque = W × 15. For equilibrium: 75 × 25 = W × 15. W = (75 × 25)/15 = 1875/15 = 125 g.
Hint
Apply principle of moments about the pivot point.