# An object travels North at  4 m/s for 7 s and then travels South at  2 m/s for  4 s. What are the object's average speed and velocity?

Jun 17, 2017

The average speed is $= 3.27 m {s}^{-} 1$
The average velocity is $= 1.82 m {s}^{-} 1$

#### Explanation:

The average speed is $=$ total distance$/$time,

The total distance is $d = \left(4 \cdot 7\right) + \left(2 \cdot 4\right) = 36 m$

The total time is $t = 7 + 4 = 11 s$

The average speed is $= \frac{d}{t} = \frac{36}{11} = 3.27 m {s}^{-} 1$

The average velocity is $=$ displacement $/ t i m e$

$\overline{v} = \frac{\Delta x}{t} = \frac{7 \cdot 4 - 2 \cdot 4}{7 + 4} = \frac{20}{11} = 1.82 m {s}^{-} 1$