passwella.
Menu

JAMB Physics 1989 Question 9

Question 9

Simple Machines

A block-and-tackle system is used to lift a load of 20 N through a vertical height of 10 m. If the efficiency of the system is 40%, how much work is done against friction?

  1. A.80 J
  2. B.120 J
  3. C.300 J
  4. D.500 J
Show the answer and explanation

Answer: C (300 J)

Explanation

Useful work = 20 × 10 = 200 J. Input = 200 ÷ 0.4 = 500 J. Work against friction = 500 − 200 = 300 J.