A car travels due east at and then immediately due west at

PHYSICS · Single correct · A Level · Physics · Mechanics and materials · Mechanics and materials

Problem

A car travels 80 km80\,\text{km} due east at 80 km h−180\,\text{km h}^{-1} and then immediately 20 km20\,\text{km} due west at 40 km h−140\,\text{km h}^{-1}. Determine the average speed for the entire journey. (a) 72 km h−172\ \text{km h}^{-1} (b) 66.7 km h−166.7\ \text{km h}^{-1} (c) 60 km h−160\ \text{km h}^{-1} (d) 40 km h−140\ \text{km h}^{-1}

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