An object travels North at 8 m/s for 9 s and then travels South at 6 m/s for 7 s. What are the object's average speed and velocity?

Jul 2, 2017

The average speed is $= 7.125 m {s}^{-} 1$ and The average velocity is $= 1.875 m {s}^{-} 1$

Explanation:

The total distance travelled is $d = 8 \cdot 9 + 6 \cdot 7 = 114 m$

The total time is $t = 9 + 7 = 16 s$

The average speed is

$\overline{v} = \frac{d}{t} = \frac{114}{16} = 7.125 m {s}^{-} 1$

The displacement is

$\Delta x = 8 \cdot 9 - 6 \cdot 7 = 30 m$

The average velocity is

$= \frac{\Delta x}{t} = \frac{30}{16} = 1.875 m {s}^{-} 1$