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hi PS Ans me physics Q!!!

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HKCEE 2001 PHYSICS PAPER 2Q2.Cautionplease give me complete formula, OK??A girl walks along a straight road from a point A to a point B with an average speed 1 ms-1. She then returns from B to A along the same road with an average speed 2 ms-1. Find the average speed of the girl for the whole... 顯示更多 HKCEE 2001 PHYSICS PAPER 2 Q2. Caution please give me complete formula, OK?? A girl walks along a straight road from a point A to a point B with an average speed 1 ms-1. She then returns from B to A along the same road with an average speed 2 ms-1. Find the average speed of the girl for the whole journey. A.zero B.0.67 ms-1 C.1.33 ms-1 D.1.41 ms-1 E.1.50 ms-1

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Let d be the distance between A and B. t be the time required to travel from A to B, then t/2 is the time to travel from B to A. Speed = distance / time So, 1 = d / t t = d Now, the total distance = 2d And the total time = t + t/2 = 3t/2 So, the average speed = total distance / total time = 2d / (3t/2) = 4d / 3d = 4/3 = 1.33 ms-1 The answer is C.

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