A car moves from X to Y with a uniform speed v₁ and returns to X with a uniform speed v₂. The average speed for this round trip is:
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Question

A car moves from X to Y with a uniform speed v₁ and returns to X with a uniform speed v₂. The average speed for this round trip is:

G1 Physics · Accepted Answer

Step 1: Let one-way distance be d. Total distance = 2d. Step 2: Total time = d/v₁ + d/v₂. Step 3: Average speed = 2d/[d/v₁ + d/v₂] = 2v₁v₂/(v₁+v₂). Final answer: D.