A fraction α of total distance D is travelled with speed v₁ and the remaining fraction with speed v₂. The average speed is:
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Question

A fraction α of total distance D is travelled with speed v₁ and the remaining fraction with speed v₂. The average speed is:

G1 Physics · Accepted Answer

Total time = αD/v₁ + (1−α)D/v₂. Hence average speed = D / total time = 1/[α/v₁ + (1−α)/v₂].