WAEC Physics 2012 Objective — Question 10
Question 10 of 50 from the West African Examinations Council (WAEC) Physics 2012 Objective paper, with the correct answer and a full explanation.
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A body of mass 120 g placed at the 10cm mark on a uniform metre rule makes the rule settle horizontally on a fulcrum placed at the 35 cm mark. Calculate the mass of the rule.
- A. A. 60 g
- B. B. 80 g
- C. C. 120 g
- D. D. 200 gCorrect
Explanation
Taking moments about the fulcrum (35cm), the metre rule's weight acts at its centre (50cm): clockwise moment = anticlockwise moment. 120x(35-10) = M(50-35) => 120x25 = Mx15 => M = 3000/15 = 200 g.
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