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JAMB Physics 1988 Question 8

Question 8

Simple Machines

A 20-toothed gear wheel drives a 60-toothed one. If the angular speed of the smaller wheel is 120 rev s−1, the angular speed of the larger wheel is

  1. A.3 rev s−1
  2. B.40 rev s−1
  3. C.360 rev s−1
  4. D.2400 rev s−1
Show the answer and explanation

Answer: B (40 rev s−1)

Explanation

The same number of teeth pass the contact point on each wheel, so speed × teeth is equal: 120 × 20 = ω × 60, giving ω = 40 rev s−1. The bigger wheel turns more slowly.