WAEC Physics 2021 Objective — Question 35
Question 35 of 50 from the West African Examinations Council (WAEC) Physics 2021 Objective paper, with the correct answer and a full explanation.
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35. A rotating disc contains a set of holes in a circle. An air jet is directed onto the holes and a note of frequency 480 Hz is produced. If the number of holes is 20, calculate the speed of rotation of the disc.
- A. 10 revs/s
- B. 20 revs/s
- C. 24 revs/sCorrect
- D. 8 revs/s
Explanation
Frequency = (revolutions/s) × (holes). So rev/s = 480/20 = 24 revs/s.
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