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JAMB Physics 2012 Question 14

Question 14

Simple Machines

A block and tackle is used to raise a load of 250N through a vertical distance of 30m. What is the efficiency of the system if the work done against friction is 1500J?

  1. A.62.5%
  2. B.73.3%
  3. C.83.3%
  4. D.94.3%.
Show the answer and explanation

Answer: C (83.3%)

Explanation

Useful work = 250 × 30 = 7500 J. Total work put in = 7500 + 1500 = 9000 J. Efficiency = 7500/9000 × 100% ≈ 83.3%.