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JAMB Physics 2010 Question 8

Question 8

Work, Energy and Power

A bob of weight 0.1 N hangs from a massless string of length 50 cm. A variable horizontal force which increases from zero is applied to pull the bob until the string makes an angle of 60° with the vertical. The work done is

  1. A.0.250 J.
  2. B.0.025 J.
  3. C.0.050 J.
  4. D.0.500 J.
Show the answer and explanation

Answer: B (0.025 J.)

Explanation

The bob rises h = L(1 − cos 60°) = 0.5 × 0.5 = 0.25 m. Work done = gain in potential energy = 0.1 × 0.25 = 0.025 J.