Physics

Problem

A car travels

80\,\text{km}

due east at

80\,\text{km h}^{-1}

and then immediately

20\,\text{km}

due west at

40\,\text{km h}^{-1}

. Determine the average speed for the entire journey. a)

72\ \text{km h}^{-1}

66.7\ \text{km h}^{-1}

60\ \text{km h}^{-1}

40\ \text{km h}^{-1}