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JAMB Physics 1998 Question 8

Question 8

Equilibrium of Forces

A uniform metre rule weighing 0.5 N is to be pivoted on a knife-edge at the 30 cm-mark. Where will a force of 2 N be placed from the pivot to balance the metre rule?

  1. A.95 cm
  2. B.25 cm
  3. C.20 cm
  4. D.5 cm
Show the answer and explanation

Answer: D (5 cm)

Explanation

The weight acts at the 50 cm mark, 20 cm from the pivot: moment = 0.5 × 20 = 10 N cm. The 2 N force must be 10 ÷ 2 = 5 cm from the pivot on the other side.