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JAMB Physics 1997 Question 11

Question 11

Equilibrium of Forces

A uniform light beam XZ is hinged at X and kept in equilibrium by the forces T and F as shown in the diagram above. If XO = 20 cm and OY = 30 cm, express T in terms of F.

Diagram for this question
  1. A.T = (2√3/3)F
  2. B.T = 2F
  3. C.T = (5√3/3)F
  4. D.T = 5F
Show the answer and explanation

Answer: D (T = 5F)

Explanation

Take moments about X. T acts at O, 20 cm away, at 30° to the beam, so its moment is T sin 30° × 20 = 10T. F acts at Y, 50 cm away: 10T = 50F, so T = 5F.