Two pointers rotate uniformly in the same direction. Pointer A completes one revolution in 20 s and pointer B in 30 s. Starting together, they next coincide after:
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Two pointers rotate uniformly in the same direction. Pointer A completes one revolution in 20 s and pointer B in 30 s. Starting together, they next coincide after:

G1 Physics · Accepted Answer

Angular frequencies are 1/20 rev/s and 1/30 rev/s. Relative frequency = 1/20−1/30 = 1/60 rev/s. Hence one full relative revolution, and therefore the next coincidence, occurs after 60 s.