JAMB - Physics (2025 - No. 30)
The figure shows a uniform metre rule of weight 100 N balanced by a knife edge at the 10 cm mark and a cord attached at the 85 cm mark. What is the tension in the string?
23.62 N
53.33 N
35.74 N
78.68 N
Explanation
Answer: B
For equilibrium, clockwise moment = anticlockwise moment about the pivot.
clockwise distance from pivot: 50cm - 10cm = 40cm
anticlockwise distance from pivot: 85cm - 10cm = 75cm
Applying the principle of moments
W x distance(w) = T x distance(T)
100 x 40 = T x 75
T = \(\frac{ 4000}{75}\) ≈ 53.33N
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