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JAMB Physics 1985 Question 10

Question 10

Equilibrium of Forces

Two masses 40 g and 60 g respectively, are attached firmly to the ends of a light metre rule. The centre of gravity of the system is

  1. A.at the mid-point of the metre rule
  2. B.40 cm from the lighter mass
  3. C.40 cm from the heavier mass
  4. D.60 cm from the heavier mass
  5. E.indeterminate because the metre-rule is light.
Show the answer and explanation

Answer: C (40 cm from the heavier mass)

Explanation

Taking moments from the lighter mass: x = (60 × 100)/100 = 60 cm from the 40 g mass, which is 40 cm from the heavier mass.