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JAMB Physics 1979 Question 2

Question 2

Simple Machines

Which of the following statements defines correctly the efficiency of a machine?

  1. A.The load carried by the machine divided by effort required in carrying the load
  2. B.The distance moved by the load divided by the distance moved by the effort
  3. C.The useful work done by the machine divided by the total work put into it.
  4. D.The movement of the load divided by the movement of the effort about the same point
  5. E.The temperature at the end of the application of the machine divided by the initial temperature.
Show the answer and explanation

Answer: C (The useful work done by the machine divided by the total work put into it.)

Explanation

Efficiency = useful work output ÷ total work input (usually × 100%). Option A is mechanical advantage and B is the inverse of velocity ratio.